Sulfonium salt compound, photoacid generator, and positive-tone radiation-sensitive resin composition

ABSTRACT

A sulfonium salt compound excelling in transparency to deep ultraviolet rays at a wavelength of 220 nm or less, exhibiting well-balanced excellent performance such as sensitivity, resolution, pattern form, LER, and storage stability when used as a photoacid generator, a photoacid generator comprising the sulfonium salt compound, and a positive-tone radiation-sensitive resin composition containing the photoacid generator. 
     The sulfonium salt compound is shown by the following formula (I), 
                         
wherein R 1  represents a halogen atom, an alkyl group, a monovalent alicyclic hydrocarbon group, an alkoxyl group, or —OR 3  group, wherein R 3  is a monovalent alicyclic hydrocarbon group, R 2  represents a (substituted)-alkyl group or two or more R 2  groups form a cyclic structure, p is 0-7, q is 0-6, n is 0-3, and X −  indicates a sulfonic acid anion.
 
     The positive-tone radiation-sensitive resin composition comprises (A) a photoacid generator of the sulfonium-salt compound and (B) an acid-dissociable group-containing resin.

TECHNICAL FIELD

The present invention relates to a novel sulfonium salt compoundsuitable as a photoacid generator used in a positive-toneradiation-sensitive resin composition useful for microprocessing usingvarious types of radiation, in particular, such as deep ultravioletradiation, electron beams, and X-rays, a photoacid generator comprisingthe sulfonium salt compound, and a positive-tone radiation-sensitiveresin composition containing the photoacid generator.

BACKGROUND ART

In the field of microfabrication represented by fabrication ofsemiconductor devices, a microfabrication technology enablingfabrication with a line width of less than 0.20 μm has been demanded tocope with the recent trend of high integration.

Use of light sources emitting a shorter wavelength light can bementioned as a method for attaining such miniaturization of patterns. Inthese days, a KrF excimer laser (wavelength: 248 nm), an ArF excimerlaser (wavelength: 193 nm), an F₂ excimer laser (wavelength: 157 nm),and EUV (wavelength: 13 nm, etc.) are more abundantly used instead ofconventional light sources such as a g-line and i-line.

In regard to the photoresist material used with such light sourcesemitting a shorter wavelength light, it is difficult for a photoresistcontaining a novolac resin and naphthoquinone diazido conventionallyused with a g-line or i-line to form fine patterns because of formationof tapered patterns due to strong absorption in the deep ultraviolet rayregion. Moreover, since this type of photoresist exhibits only a lowsensitivity of no more than 1, in terms of a quantum yield, the life ofthe excimer laser oscillation gas is short in the photo reaction duringexposure to light. This causes a problem in the life of a lens, when thelens is used with a photoresist by which the lens is easily damaged bythe excimer laser.

As a photoresist suitable for an excimer laser solving these problems,many chemically-amplified photoresists comprising a resin which causes achemical reaction accompanied by change in solubility in a developer inthe presence of an acid catalyst and a photoacid generator whichgenerates an acid upon exposure with light have been proposed.

A widely known typical example of such a chemically-amplifiedphotoresist for a KrF excimer laser comprises a resin containingpolyhydroxystyrene in which the phenolic hydroxyl groups are protectedby acid-dissociable groups such as an acetal group and t-butoxy carbonylgroup and a photoacid generator such as a triaryl sulfonium saltrepresented by a triphenylsulfonium salt (Japanese Patent ApplicationLaid-open No. 59-45439, for example).

The resin having the polyhydroxystyrene as a base skeleton used for aKrF excimer laser is not suitable as a chemically-amplified photoresistfor an ArF excimer laser because of the strong absorption of light at awavelength of 193 nm. Resin components such as a (meth)acrylate resinhaving an alicyclic skeleton, a polymer of norbornene derivatives havingan alicyclic skeleton in the main chain, and a copolymer of a norbornenederivative and a maleic anhydride have been proposed as achemically-amplified photoresist for an ArF excimer laser. On the otherhand, a triaryl sulfonium salt, when used as a photoacid generator evenin a comparatively small amount, reduces radiation transmittance of aresist due to the strong absorption by aromatic rings, even if the aboveresins are used as a resist. For this reason, the resist has problems inits performance such as difficulty in obtaining high resolution andformation of tapered pattern shape, unless the amount is unduly limited.The triaryl sulfonium salt thus is not always a suitable photoacidgenerator when an ArF excimer laser is used as radiation.

To overcome the problem of the triaryl sulfonium salt due to its lowradiation transmittance, Japanese Patent Application Laid-open No.2001-354669, for example, proposed other sulfonium salts such as asulfonium salt containing a 2-oxoalkyl group. This type of sulfoniumsalt, however, significantly decreases sensitivity although transparencyto radiation is remarkably improved. Therefore, practical sensitivitycannot always be obtained. Moreover, when the amount of the additive toimprove the anti-basic property of the photoresist or the selection ofthe additive is not appropriate, the storage stability of thephotoresist is impaired.

Japanese Patent Application Laid-open No. 10-232490 discloses aphotoacid generator of a cyclic sulfonium salt containing a substitutedor unsubstituted naphthyl group and a radiation-sensitive resincomposition containing the photoacid generator. The transmissivity ofthe sulfonium salt having this-type of structure at a wavelength of 220nm is disclosed. The resist was confirmed to exhibit excellentsensitivity and pattern shape when an ArF excimer laser was used, and tohave good storage stability. However, since many of these compounds havean absorption peak near the wavelength of 193 nm, the effect of theabsorption on radiation transmittance cannot be neglected when used in achemically-amplified photoresist to be exposed to an ArF excimer laser.The amount of the compound that can be added is limited. Moreover,cyclic sulfonium salts, particularly those having a sulfur atom directlybonded to the α-position of a naphthyl group, tend to be decomposed by adark reaction accompanied by a ring-opening reaction due to the sterichindrance of the naphthyl group, thus causing a problem in respect tostorage stability of the resist solutions.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a sulfonium saltcompound excelling in transparency to deep ultraviolet rays at awavelength of 220 nm or less, exhibiting well-balanced excellentperformance such as sensitivity, resolution, pattern form, line edgeroughness (hereinafter referred to as “LER”), storage stability, and thelike when used as a photoacid generator, a photoacid generatorcomprising the sulfonium salt compound, and a positive-toneradiation-sensitive resin composition containing the photoacidgenerator.

As a result of synthesis and detailed performance evaluation of varioussulfonium salt compounds which have not been conventionally synthesized,the present inventors have found that a sulfonium salt compoundcontaining a naphthalene ring of which the β-position is bonded by asulfur atom exhibits excellent transparency to light with a wavelengthof 220 nm or less and can overcome the above-mentioned problems in priorart technologies when used as a radiation-sensitive resin composition.These findings have led to the completion of the present invention.

The above object can be achieved in the present invention by a sulfoniumsalt compound (hereinafter referred to as “sulfonium salt compound (I)”represented by the following formula (I):

wherein R¹ represents a halogen atom, a linear or branched alkyl grouphaving 1-14 carbon atoms, a monovalent hydrocarbon group having analicyclic skeleton and containing 3-14 carbon atoms, a linear orbranched alkoxyl group having 1-14 carbon atoms, a group represented by—OR³ (wherein R³ is a monovalent hydrocarbon group having an alicyclicskeleton and containing 3-14 carbon atoms), a linear or branched alkylsulfanyl group having 1-14 carbon atoms, an organic sulfanyl grouphaving an alicyclic skeleton and containing 3-14 carbon atoms, a linearor branched alkane sulfonyl group having 1-14 carbon atoms, or anorganic sulfonyl group having an alicyclic skeleton and containing 3-14carbon atoms, two or more R¹ groups that may present being either thesame or different, R² represents a substituted or unsubstituted, linear,branched, or cyclic alkyl group having 1-14 carbon atoms, or two or moreR² groups bond to form a monocyclic structure having 3-14 carbon atomsor a polycyclic structure having 6-14 carbon atoms, two or more R²groups that may present being either the same or different, p is aninteger of 0-7, q is an integer of 0-6, n is an integer of 0-3, and X⁻represents a sulfonic acid anion.

The above object can be further achieved in the present invention by aphotoacid generator (hereinafter referred to as “photoacid generator(AI)”) comprising the sulfonium salt compound (I).

The above object can be further achieved in the present invention by apositive-tone radiation-sensitive resin composition comprising (A) aphotoacid generator containing the photoacid generator (AI) as anessential component and (B) an acid-dissociable group-containing resinwhich is insoluble or scarcely soluble in alkali, but becomes alkalisoluble when the acid-dissociable group dissociates.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a ¹H-NMR spectrometry spectrum of the sulfonium salt (A-1).

FIG. 2 shows a ¹H-NMR spectrometry spectrum of the sulfonium salt (A-2).

FIG. 3 shows a ¹H-NMR spectrometry spectrum of the sulfonium salt (A-3).

FIG. 4 shows a ¹H-NMR spectrometry spectrum of the sulfonium salt (A-4).

FIG. 5 shows a ¹H-NMR spectrometry spectrum of the sulfonium salt (A-5).

FIG. 6 shows a ¹H-NMR spectrometry spectrum of the sulfonium salt (A-6).

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be described in more detail below.

Sulfonium Salt Compound (I):

As examples of the halogen atom represented by R¹ in the formula (1), afluorine atom, chlorine atom, bromine atom, and iodine atom can begiven.

As a linear or branched alkyl group having 1-14 carbon atoms representedby R¹, a methyl group, ethyl group, n-propyl group, i-propyl group,n-butyl group, 2-methylpropyl group, 1-methylpropyl group, t-butylgroup, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group,n-nonyl group, n-decyl group, n-undecyl group, n-dodecyl group,t-dodecyl group, n-tridecyl group, n-tetradecyl group, and the like canbe given.

As the monovalent hydrocarbon group having an alicyclic skeleton andcontaining 3-14 carbon atoms, a cycloalkyl group such as a cyclopropylgroup, cyclobutyl group, cyclopentyl group, or cyclohexyl group; a grouphaving an alicyclic ring originating from a bridged alicyclichydrocarbon such as norbornane, bicyclo[2.2.2]octane, tricyclodecane,tetracyclododecane, or adamantane; a group obtainable by bonding of amethylene group or an alkylene group having 2-8 carbon atoms (forexample, an ethylene group, a propylene group, etc.) with thesecycloalkyl groups or the alicyclic ring (provided that the methylenegroup or alkylene group bonds with the naphthalene group of the formula(I)); and the like can be given.

As examples of the linear or branched alkoxyl group having 1-14 carbonatoms represented by R¹, a methoxy group, ethoxy group, n-propoxy group,i-propoxy group, n-butoxy group, 2-methylpropoxy group, 1-methylpropoxygroup, t-butoxy group, n-pentyloxy group, n-hexyloxy group, n-heptyloxygroup, n-octyloxy group, n-nonyloxy group, n-decyloxy group,n-undecyloxy group, n-dodecyloxy group, t-dodecyloxy group,n-tridecyloxy group, and n-tetradecyloxy group can be given.

As R³ in the —OR³ group represented by R¹, a cycloalkyl group such as acyclopropyl group, cyclobutyl group, cyclopentyl group, or cyclohexylgroup; a group having an alicyclic ring originating from a bridgedalicyclic hydrocarbon such as norbornane, tricyclodecane,bicyclo[2.2.2]octane, tetracyclododecane, or adamantane; a groupobtainable by bonding of a methylene group or an alkylene group having2-8 carbon atoms (for example, an ethylene group, a propylene group,etc.) with these cycloalkyl groups or the alicyclic ring (provided thatthe methylene group or alkylene group bonds with the oxygen atom of the—OR³ group); and the like can be given.

As the linear or branched alkyl sulfanyl group having 1-14 carbon atomsrepresented by R¹, a methyl sulfanyl group, ethyl sulfanyl group,n-propyl sulfanyl group, i-propyl sulfanyl group, n-butyl sulfanylgroup, 2-methylpropyl sulfanyl group, 1-methylpropyl sulfanyl group,t-butyl sulfanyl group, n-pentyl sulfanyl group, n-hexyl sulfanyl group,n-heptyl sulfanyl group, n-octyl sulfanyl group, n-nonyl sulfanyl group,n-decyl sulfanyl group, n-undecyl sulfanyl group, n-dodecyl sulfanylgroup, n-tridecyl sulfanyl group, n-tetradecyl sulfanyl group, and thelike can be given.

As the organic sulfanyl group having an alicyclic skeleton andcontaining 3-14 carbon atoms represented by R¹, cycloalkyl sulfanylgroups such as a cyclopropyl sulfanyl group, cyclobutyl sulfanyl group,cyclopentyl sulfanyl group, and cyclohexyl sulfanyl group; organicsulfanyl groups in which the sulfur atom directly bonds to an alicyclicring originating from a bridged alicyclic hydrocarbon such as(bicyclo[2.2.1]heptan-2-yl)sulfanyl group,(bicyclo[2.2.2]octan-2-yl)sulfanyl group,(tetracyclo[4.2.0.1^(2.5).1^(7.10)]dodecan-3-yl)sulfanyl group,(adamantan-2-yl)sulfanyl group; organic sulfanyl groups obtainable bybonding of a methylene group or an alkylene group having 2-8 carbonatoms (for example, an ethylene group, a propylene group, etc.) with acycloalkane such as cyclopropane, cyclobutane, cyclopentane, andcyclohexane or an alicyclic ring originating from a bridged alicyclichydrocarbon such as norbornane, bicyclo[2.2.2]octane, tricyclodecane,tetracyclododecane, and adamantane (provided that the methylene group oralkylene group bonds to a sulfur atom); and the like can be given.

As the linear or branched alkane sulfonyl group having 1-14 carbon atomsrepresented by R¹, a methane sulfonyl group, ethane sulfonyl group,n-propane sulfonyl group, n-propane-2-sulfonyl group, n-butane sulfonylgroup, 2-methylpropane-1-sulfonyl group, 1-methylpropane-1-sulfonylgroup, 2-methylpropane-2-sulfonyl group, n-pentane sulfonyl group,n-hexane sulfonyl group, n-heptane sulfonyl group, n-octane sulfonylgroup, n-nonane sulfonyl group, n-decane sulfonyl group, n-undecanesulfonyl group, n-dodecane sulfonyl group, n-tridecane sulfonyl group,n-tetradecane sulfonyl group, and the like can be given.

As the organic sulfonyl group having an alicyclic skeleton andcontaining 3-14 carbon atoms represented by R¹, cycloalkyl sulfonylgroups such as a cyclopropyl sulfonyl group, cyclobutyl sulfonyl group,cyclopentyl sulfonyl group, and cyclohexyl sulfonyl group; organicsulfonyl groups in which the sulfur atom directly bonds to an alicyclicring originating from a bridged alicyclic hydrocarbon such asbicyclo[2.2.1]heptane-2-sulfonyl group, bicyclo[2.2.2]octane-2-sulfonylgroup, tetracyclo[4.2.0.1^(2.5).1^(7.10)]dodecan-3-sulfonyl group, andadamantane-2-sulfonyl group; organic sulfonyl groups obtainable bybonding of a methylene group or an alkylene group having 2-8 carbonatoms (for example, an ethylene group, a propylene group, etc.) with acycloalkane such as cyclopropane, cyclobutane, cyclopentane, andcyclohexane or an alicyclic ring originating from a bridged alicyclichydrocarbon such as norbornane, bicyclo[2.2.2]octane, tricyclodecane,tetracyclododecane, and adamantane (provided that the methylene group oralkylene group bonds to a sulfur atom); and the like can be given. Thegroup R¹ in the formula (I) preferably bonds to the 6-position of thenaphthalene ring.

As the group R¹ in the formula (I), the following groups are preferable:a fluorine atom, methyl group, n-butyl group, n-pentyl group, n-hexylgroup, n-heptyl group, n-octyl group, cyclohexyl group,bicyclo[2.2.1]heptan-2-yl group, bicyclo[2.2.2]octan-2-yl group,tetracyclo[4.2.0.1^(2.5).0^(7.10)]dodec-3-yl group,(bicyclo[2.2.1]heptan-2-yl)methyl group,(bicyclo[2.2.2]octan-2-yl)methyl group,(tetracyclo[4.2.0.1^(2.5).1^(7.10)]dodecan-3-yl)methyl group, methoxygroup, n-butoxy group, n-pentyloxy group, n-hexyloxy group, n-heptyloxygroup, n-octyloxy group, cyclopentyloxy group, cyclohexyloxy group,(bicyclo[2.2.1]heptan-2-yl)oxy group, (bicyclo[2.2.2]octan-2-yl)oxygroup, (tetracyclo[4.2.0.1^(2.5).1^(7.10)]dodecan-3-yl)oxy group,cyclopentylmethoxy group, cyclohexylmethoxy group,(bicyclo[2.2.1]heptan-2-yl)methoxy group,(bicyclo[2.2.2]octan-2-yl)methoxy group,(tetracyclo[4.2.0.1^(2.5).1^(7.10)]dodecan-3-yl)methoxy group,n-butylsulfanyl group, n-pentylsulfanyl group, n-hexylsulfanyl group,n-heptylsulfanyl group, n-octylsulfanyl group, cyclopentyl sulfanylgroup, cyclohexyl sulfanyl group, (bicyclo[2.2.1]heptan-2-yl)sulfanylgroup, (bicyclo[2.2.2]octan-2-yl)sulfanyl group,(tetracyclo[4.2.0.1^(2.5).1^(7.10)]dodecan-3-yl)sulfanyl group,(bicyclo[2.2.1]heptan-2-yl)methylsulfanyl group,(bicyclo[2.2.2]octan-2-yl)methylsulfanyl group,(tetracyclo[4.2.0.1^(2.5).1^(7.10)]dodecan-3-yl)methylsulfanyl group,n-butanesulfonyl group, n-pentanesulfonyl group, n-hexanesulfonyl group,n-heptanesulfonyl group, n-octanesulfonyl group,bicyclo[2.2.1]heptane-2-sulfonyl group, bicyclo[2.2.2]octane-2-sulfonylgroup, tetracyclo[4.2.0.1^(2.5).1^(7.10)]dodecane-3-sulfonyl group,(bicyclo[2.2.1]heptan-2-yl)methanesulfonyl group,(bicyclo[2.2.2]octan-2-yl)methanesulfonyl group, and(tetracyclo[4.2.0.1^(2.5).1^(7.10)]dodecan-3-yl)methanesulfonyl group.

As the linear, branched, or cyclic alkyl group having 1-14 carbon atomsrepresented by R² in the formula (I), a methyl group, ethyl group,n-propyl group, i-propyl group, n-butyl group, 2-methylpropyl group,1-methylpropyl group, t-butyl group, n-pentyl group, n-hexyl group,n-heptyl group, n-octyl group, n-nonyl group, n-decyl group, n-undecylgroup, n-dodecyl group, t-dodecyl group, n-tridecyl group, n-tetradecylgroup, cyclopropyl group, cyclobutyl group, cyclopentyl group,cyclohexyl group, and the like can be given.

As the substituent for the substituted linear, branched, or cyclic alkylgroup having 1-14 carbon atoms represented by R², one or more groupsamong a hydroxyl group, carboxyl group, oxo group (═O), cyano group,linear or branched alkoxyl group having 1-8 carbon atoms (e.g., amethoxy group, ethoxy group, n-propoxy group, i-propoxy group, n-butoxygroup, 2-methylpropoxy group, 1-methylpropoxy group, t-butoxy group,etc.), linear or branched alkoxyalkoxy group having 2-8 carbon atoms(e.g., a methoxymethoxy group, ethoxymethoxy group, t-butoxymethoxygroup, etc.), linear or branched alkylcarbonyloxy group having 2-8carbon atoms (e.g., a methylcarbonyloxy group, ethylcarbonyloxy group,t-butylcarbonyloxy group, etc.), linear or branched alkoxycarbonyl grouphaving 2-8 carbon atoms (e.g., a methoxycarbonyl group, ethoxycarbonylgroup, t-butoxycarbonyl group, etc.), halogen atom (e.g., a fluorineatom, chlorine atom, etc.), and the like can be given.

The rings of the monocyclic structure having 3-14 carbon atoms orpolycyclic structure having 6-14 carbon atoms formed by bonding of twoor more R² groups may be either a carbon ring or a ring containing oneor more hetero atoms such as a nitrogen atom, oxygen atom, sulfur atom,etc.

The following can be given as examples of the monocyclic or polycyclicrings: ring structures originating from a cycloalkane such as acyclopropane, cyclobutane, cyclopentane, and cyclohexane; ringstructures originating from a bridged alicyclic hydrocarbon such asnorbornane, bicyclo[2.2.2]octane, tricyclodecane, tetracyclododecane,and adamantane; ring structures obtainable by substituting these ringstructures with one or more substituents selected from the groupconsisting of a hydroxyl group, carboxyl group, oxo group (═O), cyanogroup, halogen atom (e.g., a fluorine atom, a chlorine atom, etc.),linear or branched alkyl group having 1-14 carbon atoms (e.g., a methylgroup, ethyl group, n-propyl group, i-propyl group, n-butyl group,2-methylpropyl group, 1-methylpropyl group, t-butyl group, etc.), linearor branched alkoxyl group having 1-8 carbon atoms (e.g., a methoxygroup, ethoxy group, n-propoxy group, i-propoxy group, n-butoxy group,2-methylpropoxy group, 1-methylpropoxy group, t-butoxy group, etc.),linear or branched alkoxyalkyl group having 2-8 carbon atoms (e.g., amethoxymethyl group, ethoxymethyl group, t-butoxymethyl group, etc.),linear or branched alkoxyalkoxy group having 2-8 carbon atoms (e.g., amethoxymethoxy group, ethoxymethoxy group, t-butoxymethoxy group, etc.),linear or branched alkylcarbonyloxy group having 2-8 carbon atoms (e.g.,a methylcarbonyloxy group, ethylcarbonyloxy group, t-butylcarbonyloxygroup, etc.), linear or branched alkoxycarbonyl group having 2-8 carbonatoms (e.g., a methoxycarbonyl group, ethoxycarbonyl group,t-butoxycarbonyl group, etc.), linear or branched cyanoalkyl grouphaving 2-14 carbon atoms (e.g., a cyanomethyl group, 2-cyanoethyl group,3-cyanopropyl group, 4-cyanobutyl, etc.), linear or branched fluoroalkylgroup having 1-14 carbon atoms (e.g., a fluoromethyl group,trifluoromethyl group, pentafluoroethyl group, etc.), and the like canbe given.

As R² in the formula (I), an alkyl group having 1-3 carbon atoms such asa methyl group, ethyl group, n-propyl group, and i-propyl group arepreferable. As the structure formed by bonding of two or more R² groups,a cyclohexane cyclic structure, norbornane cyclic structure, andtetracyclododecane cyclic structure, either substituted or unsubstitutedby one or more of a methyl group and a hydroxyl group are preferable. Amore preferable R² group in the formula (I) is an unsubstituted groupamong the above alkyl groups and a norbornene ring structure formed bybonding of two or more R² groups. When R² is the above alkyl group, thealkyl group preferably bonds to the position next to the sulfur atom. Inthis instance, since base resistance is further improved by the sterichindrance of the alkyl group, storage stability of the positive-toneradiation-sensitive resin composition containing the photoacid generatorusing the sulfonium salt compound (I) as an essential component can beimproved.

In the formula (I), p is preferably 0-3, and particularly preferably 0or 1; q is preferably 0-2, and particularly preferably 0; and n ispreferably 1-3, and particularly preferably 2.

In another aspect of the present invention, a compound in which p is 1,q is 0, n is 2, and R¹ is a linear of branched alkoxyl group having 1-14carbon atoms or —OR³ (wherein R³ is a monovalent hydrocarbon grouphaving an alicyclic skeleton and containing 3-14 carbon atoms) andpreferably the alkoxyl group, in the formula (1) is preferable. In thisinstance, since the sulfonium salt compound (I) is stabilized byelectro-donative properties of the alkoxyl group or OR³ group, therebyfurther improving the heat resistance and base resistance, storagestability of the positive-tone radiation-sensitive resin compositioncontaining the photoacid generator using the sulfonium salt compound (I)as an essential component is improved. In this instance, the alkoxylgroup or the OR³ group preferably bonds to the 6-position of thenaphthalene ring, whereby the electro-donating effect to the sulfur atomincreases due to the resonance structure via the naphthalene ring. Thisnot only results in further improvement of the heat resistance and baseresistance, but also increases transparency in a deep-ultraviolet rayregion.

The following groups are given as examples of the sulfonic acid anionrepresented by X⁻ in the formula (I): linear or branched alkyl sulfonicacid anions such as a methanesulfonic acid anion, ethanesulfonic acidanion, n-propanesulfonic acid anion, n-butanesulfonic acid anion,n-pentanesulfonic acid anion, and n-hexanesulfonic acid anion; alicyclicsulfonic acid anions such as a cyclohexane sulfonic acid anion andd-camphor-10-sulfonic acid anion; aromatic sulfonic acid anions such asbenzenesulfonic acid anion, p-toluenesulfonic acid anion,4-methoxybenzenesulfonic acid anion, 4-n-octylbenzenesulfonic acidanion, 1-naphthalenesulfonic acid anion, 2-naphthalenesulfonic acid,pyrene-2-sulfonic acid anion, 9-anthracenesulfonic acid anion, and9,10-dimethoxyanthracene-2-sulfonic acid anion; fluorine-substitutedbenzenesulfonic acid anion such as 4-fluorobenzenesulfonic acid anion,3-fluorobenzenesulfonic acid anion, 2-fluorobenzenesulfonic acid anion,2,4-difluorobenzenesulfonic acid, 3,5-difluorobenzenesulfonic acid,3,4,5-trifluorobenzenesulfonic acid, and perfluorobenzenesulfonic acid;aromatic sulfonic acid anions having an electron-drawing substituentsuch as a 4-trifluoromethylbenzenesulfonic acid anion,3-trifluoromethylbenzenesulfonic acid anion,2-trifluoromethylbenzenesulfonic acid anion,2,4-bis(trifluoromethyl)benzenesulfonic acid, and3,5-bis(trifluoromethyl)phenylbenzenesulfonic acid anion;1,1-difluoroalkyl sulfonic acid anions such as1,1-difluoroethanesulfonic acid anion, 1,1-difluoro-n-propanesulfonicacid anion, 1,1-difluoro-n-butanesulfonic acid anion,1,1-difluoro-n-octanesulfonic acid anion,2-cyclohexyl-1,1-difluoroethanesulfonic acid anion, and2-(bicyclo[2.2.1]heptan-2-yl)-1,1-difluoroethane sulfonic-acid anion;trifluoromethansulfonic acid anion, a sulfonic acid anion of thefollowing formula (II) (hereinafter referred to as “sulfonic-acid anion(II)”),R⁴—CF₂CF₂SO₃ ⁻  (II)wherein R⁴ represents a substituted or unsubstituted, linear or branchedalkyl group having 1-14 carbon atoms or a substituted or unsubstituted,monovalent hydrocarbon group with 3-14 carbon atoms having an alicyclicring.

As the unsubstituted linear or branched alkyl group having 1-14 carbonatoms represented by R⁴ in the formula (II), a methyl group, ethylgroup, n-propyl group, i-propyl group, n-butyl group, 2-methylpropylgroup, 1-methylpropyl group, t-butyl group, n-pentyl group, n-hexylgroup, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group,n-undecyl group, n-dodecyl group, t-dodecyl group, n-tridecyl group,n-tetradecyl group, and the like can be given.

As the unsubstituted monovalent hydrocarbon group having an alicyclicskeleton and containing 3-14 carbon atoms represented by R⁴, acycloalkyl group such as a cyclopropyl group, cyclobutyl group,cyclopentyl group, or cyclohexyl group; a group having an alicyclic ringoriginating from a bridged alicyclic hydrocarbon such as norbornane,bicyclo[2.2.2]octane, tricyclodecane, tetracyclododecane, or adamantane;a group obtainable by bonding of a methylene group or an alkylene grouphaving 2-8 carbon atoms (e.g., an ethylene group, propylene group, etc.)with these cycloalkyl groups or the alicyclic ring (provided that themethylene group or alkylene group bonds with the tetrafluoroethylenegroup of the formula (II)); and the like can be given.

As the substituent for the substituted linear or branched alkyl grouphaving 1-14 carbon atoms represented by R⁴, one or more groups among ahydroxyl group, carboxyl group, oxo group (═O), cyano group, halogenatom (e.g., a fluorine atom, chlorine atom, etc.), linear or branchedalkoxyl group having 1-8 carbon atoms (e.g., a methoxy group, ethoxygroup, n-propoxy group, i-propoxy group, n-butoxy group, 2-methylpropoxygroup, 1-methylpropoxy group, t-butoxy group, etc.), linear or branchedalkoxyalkoxyl group having 2-8 carbon atoms (e.g., a methoxymethoxygroup, ethoxymethoxy group, t-butoxymethoxy group, etc.), linear orbranched alkylcarbonyloxy group having 2-8 carbon atoms (e.g., amethylcarbonyloxy group, ethylcarbonyloxy group, t-butylcarbonyloxygroup, etc.), linear or branched alkoxycarbonyl group having 2-8 carbonatoms (e.g., a methoxycarbonyl group, ethoxycarbonyl group,t-butoxycarbonyl group, etc.), and the like can be given. A fluorineatom is preferable among these.

As the substituent for the substituted monovalent hydrocarbon grouphaving an alicyclic structure and containing 3-14 carbon atomsrepresented by R⁴, one or more groups among a hydroxyl group, carboxylgroup, oxo group (═O), cyano group, halogen atom (e.g., a fluorine atom,chlorine atom, etc.), linear or branched alkyl group having 1-14 carbonatoms (e.g., a methyl group, ethyl group, n-propyl group, i-propylgroup, n-butyl group, 2-methylpropyl group, 1-methylpropyl group,t-butyl group, etc.), linear or branched alkoxyl group having 1-8 carbonatoms (e.g., a methoxy group, ethoxy group, n-propoxy group, i-propoxygroup, n-butoxy group, 2-methylpropoxy group, 1-methylpropoxy group,t-butoxy group, etc.), linear or branched alkoxyalkyl group having 2-8carbon atoms (e.g., a methoxymethyl group, ethoxymethyl group,t-butoxymethyl group, etc.), linear or branched alkoxyalkoxyl grouphaving 2-8 carbon atoms (e.g., a methoxymethoxy group, ethoxymethoxygroup, t-butoxymethoxy group, etc.), linear or branchedalkylcarbonyloxyl group having 2-8 carbon atoms (e.g., amethylcarbonyloxy group, ethylcarbonyloxy group, t-butylcarbonyloxygroup, etc.), linear or branched alkoxycarbonyl group having 2-8 carbonatoms (e.g., a methoxycarbonyl group, ethoxycarbonyl group,t-butoxycarbonyl group, etc.), linear or branched cyanoalkyl grouphaving 2-8 carbon atoms (e.g., a cyanomethyl group, 2-cyanoethyl group,3-cyanopropyl group, 4-cyanobutyl, etc.), linear or branchedalkoxycarbonyloxy group having 2-8 carbon atoms (e.g., amethoxycarbonyloxy group, ethoxycarbonyloxy group, i-propoxycarbonyloxygroup, t-butoxycarbonyloxy group, etc.), and the like can be given.

Particularly preferable groups represented by R⁴ in the formula (II) area pentafluoro ethyl group, perfluoro-n-hexyl group,bicyclo[2.2.1]heptan-2-yl group, and the like.

Among the above sulfonic acid anions, the sulfonic acid anions (II),particularly, nonafluoro-n-butane sulfonic acid anion,perfluoro-n-octane sulfonic acid anion,2-(bicyclo[2.2.1]heptan-2-yl)-1,1,2,2-tetrafluoroethane sulfonic acidanion, and the like are preferable.

Specific examples of sulfonium salt compound (I) include:nonafluoro-n-butanesulfonates such as

-   1-(naphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-methylnaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-n-butyl-naphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-n-pentylnaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-n-hexylnaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-n-heptylnaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-n-octylnaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-cyclopentylnaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-cyclohexylnaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-[6-(bicyclo[2.2.1]heptan-2-yl)naphthalen-2-yl]tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-[6-(bicyclo[2.2.2]octan-2-yl)naphthalen-2-yl]tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-[6-(tetracyclo[4.2.0.1^(2.5).1^(7.10)]dodecan-3-yl)naphthalen-2-yl]tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-[(6-cyclopentylmethyl)naphthalen-2-yl]tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-[(6-cyclohexylmethyl)naphthalen-2-yl]tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-[6-{(bicyclo[2.2.1]heptan-2-yl)methyl}naphthalen-2-yl]tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-[6-{(bicyclo[2.2.2]octan-2-yl)methyl}naphthalen-2-yl]tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-[6-{(tetracyclo[4.2.0.1^(2.5).1^(7.10)]dodecan-3-yl)methyl}naphthalen-2-yl]-tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-methoxynaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-n-butoxynaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-n-pentyloxynaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-n-hexyloxynaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-n-heptyloxynaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-n-octyloxynaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-cyclopentyloxynaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-cyclohexyloxynaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-[6-(bicyclo[2.2.1]heptan-2-yloxy)naphthalen-2-yl]tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-[6-(bicyclo[2.2.2]octan-2-yloxy)naphthalen-2-yl]tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-[6-(tetracyclo[4.2.0.1^(2.5).1^(7.10)]dodecan-3-yloxy)naphthalen-2-yl]tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-cyclopentylmethoxynaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-cyclohexylmethoxynaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-[6-(bicyclo[2.2.1]heptan-2-ylmethoxy)naphthalen-2-yl]tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-[6-(bicyclo[2.2.2]octan-2-ylmethoxy)naphthalen-2-yl]tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-[6-(tetracyclo[4.2.0.1^(2.5).1^(7.10)]dodecan-3-ylmethoxy)naphthalen-2-yl]-tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-methylsulfanylnaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-n-butylsulfanylnaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-n-pentylsulfanylnaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-n-hexylsulfanylnaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-n-heptylsulfanylnaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-n-octylsulfanylnaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-cyclopentylsulfanylnaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-cyclohexylsulfanylnaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-[6-{(bicyclo[2.2.1]heptan-2-yl)sulfanyl}naphthalen-2-yl]tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-[6-{(bicyclo[2.2.2]octan-2-yl)sulfanyl}naphthalen-2-yl]tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-[6-{(tetracyclo[4.2.0.1^(2.5).1^(7.10)]dodecan-3-yl)sulfanyl}naphthalen-2-yl]-tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-cyclopentylmethoxynaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-cyclohexylmethoxynaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-[6-(bicyclo[2.2.1]heptan-2-ylmethoxy)naphthalen-2-yl]tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-[6-(bicyclo[2.2.2]octan-2-ylmethoxy)naphthalen-2-yl]tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-[6-(tetracyclo[4.2.0.1^(2.5).1^(7.10)]dodecan-3-ylmethoxy)naphthalen-2-yl]-tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-methanesulfonylnaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-ethanesulfonylnaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-n-buthanesulfonylnaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-n-pentanesulfonylnaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-n-hexanesulfonylnaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-n-heptanesulfonylnaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-n-octanesulfonylnaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-cyclopentanesulfonylnaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-cyclohexanesulfonylnaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-[6-(bicyclo[2.2.1]heptan-2-sulfonyl)naphthalen-2-yl]tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-[6-(bicyclo[2.2.2]octan-2-sulfonyl)naphthalen-2-yl]tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-[6-(tetracyclo[4.2.0.1^(2.5).1^(7.10)]dodecan-3-sulfonyl)naphthalen-2-yl]-tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-[6-(bicyclo[2.2.1]heptan-2-yl)methanesulfonylnaphthalen-2-yl]tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-[6-(bicyclo[2.2.2]octan-2-yl)methanesulfonylnaphthalen-2-yl]tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-[6-(tetracyclo[4.2.0.1^(2.5).1^(7.10)]dodecan-3-yl)methanesulfonylnaphthalen-2-yl]-tetrahydrothiophenium    nonafluoro-n-butanesulfonate, and compounds obtainable by replacing    a nonafluoro-n-butanesulfonic acid anion in these    nonafluoro-n-butane sulfonates with a perfluoro-n-octanesulfonic    acid anion or-   2-(bicyclo[2.2.1]heptan-2-yl)-1,1,2,2,-tetrafluoroethanesulfonic    acid anion.

Of these sulfonium-salt compounds (I), the following compounds arepreferable:

-   1-(6-methoxynaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-n-butoxynaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-n-pentyloxynaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-n-hexyloxynaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-n-heptyloxynaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-n-octyloxynaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-cyclopentyloxynaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-cyclohexyloxynaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-[6-(bicyclo[2.2.1]heptan-2-yloxy)naphthalen-2-yl]tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-[6-(bicyclo[2.2.2]octan-2-yloxy)naphthalen-2-yl]tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-[6-(tetracyclo[4.2.0.1^(2.5).1^(7.10)]dodecane-3-yloxy)naphthalen-2-yl]-tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-cyclopentylmethoxynaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-(6-cyclohexylmethoxynaphthalen-2-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-[6-(bicyclo[2.2.1]heptan-2-ylmethoxy)naphthalen-2-yl]tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-[6-(bicyclo[2.2.2]octan-2-ylmethoxy)naphthalen-2-yl]tetrahydrothiophenium    nonafluoro-n-butanesulfonate,-   1-[6-(tetracyclo[4.2.0.1^(2.5).1^(7.10)]dodecan-3-ylmethoxy)naphthalen-2-yl]-tetrahydrothiophenium    nonafluoro-n-butanesulfonate, and compounds obtainable by replacing    a nonafluoro-n-butanesulfonic acid anion in these    nonafluoro-n-butane sulfonates with a perfluoro-n-octanesulfonic    acid anion or-   2-(bicyclo[2.2.1]heptan-2-yl)-1,1,2,2,-tetrafluoroethanesulfonic    acid anion.

The onium salt compound (I) is not only extremely suitable for use as aphotoacid generator responsive to active radiations such as deepultraviolet rays represented by a KrF excimer laser, ArF excimer laser,F₂ excimer laser, and EUV, as well as to electron beams, in aradiation-sensitive resin composition useful as a chemically amplifiedphotoresist in the field of microfabrication represented by themanufacture of semiconductor devices, but is also useful as a rawmaterial for the synthesis of a heat acid generator which generates anacid with heating and other related onium salt compounds.

Synthesis of Sulfonium Salt Compound (I)

The sulfonium compound (I) can be manufactured by, for example, aprocess shown by the following reaction formula (a) or (b), wherein nand X⁻ are respectively the same as the n and X⁻ in the formula (I), Xrepresents an atom or atomic group providing X⁻, and Z is a dissociablesubstituent such as a halogen and a sulfonate. In the formulas,substituents R¹ and R² are omitted.

In the reaction formula (a), 2-naphthalene thiol (i) is reacted withα-chloro-ω-alkanol (ii) in the presence of an organic base such astriethylamine to obtain 2-(ω-hydroxyalkyl sulfanyl)naphthalene (iii).The 2-(ω-hydroxyalkyl sulfanyl)naphthalene (iii) is then reacted withmethanesulfonyl chloride in the presence of an organic base to obtain amethansulfonic acid ester (iv). The methansulfonic acid ester (iv) isthen cyclized with heating and converted into a sulfonium methanesulfonate salt, which is reacted with an ammonium salt or an alkalimetal salt of X⁻ for ion-exchange, thereby obtaining the sulfonium-saltcompound (I).

The 2-naphthalene thiol used in the reaction formula (a) can be preparedusing, for example, a method of transforming 2-naphthalene sulfonic acidinto sulfonyl chloride using a chlorinating agent and reducing thesulfonyl chloride (see J. Org. Chem., Vol. 57, p. 2631-2641(1992),Liebigs Ann. Chem., p. 1112-1140(1973)), a method of directly reducing2-naphthalene sulfonic acid (see Bull. Chem. Soc. Jpn., p. 3802-3812(1983)), a method of using a nucleophilic substitution reaction of2-naphthyl diazonium salt and a sulfur anion (see J. Prakt. Chim., Vol.41, p. 218 (1890)), a method of transforming a 2-halogenated naphthaleneinto a corresponding organolithium compound or a corresponding Grignardreagent and reacting with sulfur (see Bull. Soc. Chim. Belg., Vol. 65,p. 874-891 (1956)), and a method of reacting 2-bromonaphthalene with alow-alkyl thiorate (see Synthesis, p. 751-755 (1983)).

In the reaction formula (b), a cyclic thioether (vii) obtained by thenucleophilic substitution reaction of α,ω-disubstituted alkane (vi) andsodium sulfide is oxidized with an equivalent amount of hydrogenperoxide in the presence of a catalytic amount of sodium tungstate at 0°C. to obtain a cyclic sulfoxide (viii). After reacting the cyclicsulfoxide (viii) with trimethylsilyl trifluoromethane sulfonate at a lowtemperature of about −78° C. according to the method described in J.Org. Chem., Vol. 43, p. 5571-5573 (1988), for example, the reactionproduct is reacted with a Grignard reagent (ix), then with an acid (x)to obtain the sulfonium salt compound (I).

Each reaction is usually carried out in an appropriate solvent.

As the solvent, an appropriate solvent is selected from among water,methanol, ethanol, acetone, dichloromethane, tetrahydrofuran,acetonitrile, 1-methylpyrrolidone, N,N-dimethylformamide, adichloromethane-tetrahydrofuran mixed solvent, diethyl ether, benzene,toluene, a diethyl-ether-toluene mixed solvent, a diethyl-ether-benzenemixed solvent, and the like.

Photoacid Generator

The photoacid generator of the present invention, which is an sulfoniumsalt compound (I), generates an acid when exposed to radiation, and issuitably used as a photoacid generator for a radiation-sensitive resincomposition useful for microfabrication utilizing various types ofradiation represented by deep ultraviolet rays such as a KrF excimerlaser, ArF excimer laser, F₂ excimer laser, and EUV, and electron beams.Hereinafter, the photoacid generators of the sulfonium salt compound (I)will be referred to as “acid generator (A1)”.

Positive-tone Radiation-sensitive Resin Composition

Acid Generator (A)

The component (A) of the positive-tone radiation-sensitive resincomposition of the present invention is a photoacid generator(hereinafter referred to as “acid generator (A)”) comprising thephotoacid generator (A1) as an essential component.

The acid generator (A1) can be used either individually or incombination of two or more in the positive-tone radiation sensitiveresin composition of the present invention.

One or more photoacid generators other than the acid generator (A1)(hereinafter referred to as “other acid generators”) can be used incombinations in the positive-tone radiation-sensitive resin compositionof the present invention.

As examples of the other acid generators, onium salt compounds, sulfonecompounds, sulfonate compounds, sulfonimide compounds, diazomethanecompounds, disulfonylmethane compounds, oximesulfonate compound, and thelike can be given.

As examples of onium salt compounds, iodonium salts, sulfonium salts(including tetrahydrothiophenium salts), phosphonium salts, diazoniumsalts, ammonium salts, pyridinium salts, and the like can be given.

As examples of the sulfone compound, β-ketosulfone, β-sulfonylsulfone,and α-diazo compounds of these compounds can be given.

As examples of the sulfonate compound, alkyl sulfonate, haloalkylsulfonate, aryl sulfonate, and imino sulfonate can be given.

As an example of the sulfonimide compound, a compound of the followingformula (1), and the like can be given:

wherein Y is a divalent organic group and R⁵ is a monovalent organicgroup.

As examples of Y in the formula (1), a methylene group, linear orbranched alkylene group having 2-20 carbon atoms, aralkylene grouphaving 2-20 carbon atoms, difluoromethylene group, linear or branchedperfluoroalkylene group having 2-20 carbon atoms, cyclohexylene group,phenylene group, substituted or unsubstituted divalent group possessinga norbornene skeleton, or a group wherein these groups are substitutedwith an aryl group having six or more carbon atoms or an alkoxyl grouphaving one or more carbon atoms can be given.

As examples of R⁵, a linear or branched alkyl group having 1-10 carbonatoms, linear or branched perfluoroalkyl group having 1-10 carbon atoms,perfluorocycloalkyl group having 3-10 carbon atoms, monovalenthydrocarbon group possessing a bicyclo ring having 7-15 carbon atoms,and an aryl group having 6-12 carbon atoms, can be given.

As an example of the diazomethane compound, a compound of the followingformula (2), and the like can be given:

wherein R⁶ individually represents a monovalent group such as a linearor branched alkyl group, cycloalkyl group, aryl group, halogenated alkylgroup, halogenated cycloalkyl group, and halogenated aryl group.

As an example of the disulfonylmethane compound, a compound of thefollowing formula (3) can be given:

wherein R⁷ individually represents a linear or branched monovalentaliphatic hydrocarbon group, cycloalkyl group, aryl group, aralkylgroup, other monovalent organic group having a hetero atom, V and Windividually represent an aryl group, hydrogen atom, a linear orbranched monovalent aliphatic hydrocarbon group, a cycloalkyl group,aralkyl group, or other monovalent organic group having a hetero atom,provided that at least one of V and W represents an aryl group, or V andW bond to form a monocyclic or polycyclic ring having at least oneunsaturated bond, or V and W bond to form a group shown by the followingformula (4);

wherein V's and W's individually represent a hydrogen atom, halogenatom, linear or branched alkyl group, cycloalkyl group, aryl group, oraralkyl group, or V′ and W′, each bonded to the same or different carbonatoms, may form a monocarbocyclic structure, and j is an integer from 2to 10.

As examples of the oxime sulfonate compound, compounds of the followingformula (5-1) or (5-2) can be given:

wherein R⁸ and R⁹ individually represent a monovalent organic group.

As specific examples of R⁸ in the formulas (5-1) and (5-2), a methylgroup, ethyl group, n-propyl group, phenyl group, and tosyl group can begiven. As specific examples of R⁹, a phenyl group, tosyl group,1-naphthyl group, trifluoromethyl group, and nonafluoro-n-butyl groupcan be given.

At least one acid generator selected from the group consisting of anonium salt compound, sulfonimide compound, and diazomethane compound ispreferably used as the other acid generator.

As specific preferable examples of the other acid generator, at leastone compounds selected from the group consisting of:

-   bis(4-t-butylphenyl)iodonium trifluoromethane sulfonate,-   bis(4-t-butylphenyl)iodonium nonafluoro-n-butanesulfonate,-   bis(4-t-butylphenyl)iodonium p-toluenesulfonate,-   bis(4-t-butylphenyl)iodonium 10-camphorsulfonate,-   bis(4-t-butylphenyl)iodonium 2-trifluoromethylbenzenesulfonate,-   bis(4-t-butylphenyl)iodonium 4-trifluoromethylbenzenesulfonate,-   bis(4-t-butylphenyl)iodonium 2,4-difluorobenzenesulfonate,-   triphenylsulfonium trifluoromethanesulfonate,-   triphenylsulfonium nonafluoro-n-butanesulfonate,-   triphenylsulfonium p-toluenesulfonate,-   triphenylsulfonium 10-camphorsulfonate,-   triphenylsulfonium 2-trifluoromethylbenzenesulfonate,-   triphenylsulfonium 4-trifluorobenzenesulfonate,-   triphenylsulfonium 2,4-difluorobenzenesulfonate,-   4-fluorophenyl.diphenylsulfonium nonafluoro-n-butanesulfonate,-   4-methoxyphenyl.diphenylsulfonium nonafluoro-n-butanesulfonate,-   4-n-butanesulfonyloxyphenyl.diphenylsulfonium    nonafluoro-n-butanesulfonate,-   4-cyclohexylphenyl.diphenylsulfonium nonafluoro-n-butanesulfonate,-   4-t-butylphenyl.diphenylsulfonium nonafluoro-n-butanesulfonate,-   4-n-butanesulfonylphenyl.diphenylnonafluoro-n-butanesulfonate,-   4-cyclohexanesulfonylphenyl.diphenylsulfonium    nonafluoro-n-butanesulfonate,-   2-methylphenyl.diphenylnonafluoro-n-butanesulfonate,-   2,4-dimethylphenyl.diphenylnonafluorobutanesulfonate,-   mesityl.diphenylsulfonium nonafluoro-n-butanesulfonate,-   1-(4-n-butoxynaphthalen-1-yl)tetrahydrothiophenium    trifluoromethanesulfonate,-   1-(4-n-butoxynaphthalen-1-yl)tetrahydrothiophenium    nonafluoro-n-butanesulfonate,    compounds of the formulas (6-1) to (6-8) (wherein n-C₄F₉SO₃ ⁻ is a    nonafluoro-n-butanesulfonate anion),

-   N-(trifluoromethanesulfonyloxy)succinimide,-   N-(trifluoromethanesulfonyloxy)bicyclo[2.2.1]hept-5-ene-2,3-dicarboxyimide,-   N-(10-camphorsulfonyloxy)succinimide,-   N-(10-camphorsulfonyloxy)bicyclo[2.2.1]hept-5-ene-2,3-dicarboxyimide,-   N-[(5-methyl-5-carboxymethylbicyclo[2.2.1]hept-2-yl)sulfonyloxy]succinimide,-   bis(cyclohexanesulfonyl)diazomethane,-   bis(t-butylsulfonyl)diazomethane, and-   bis(1,4-dioxaspiro[4.5]-decane-7-sulfonyl)diazomethane can be given.

The proportion of other acid generators can be appropriately determineddepending on the types of each acid generator. The proportion is 95parts by weight or less, preferably 90 parts by weight or less, andparticularly preferably 80 parts by weight or less for 100 parts byweight of the total amount of the acid generator (A1) and the other acidgenerators. If the proportion of the other acid generators exceeds 95parts by weight, the desired effects of the present invention may beimpaired.

(B) Acid-dissociable Group-containing Resin

The component (B) of the positive-tone radiation sensitive resincomposition of the present invention is an acid-dissociablegroup-containing resin which is insoluble or scarcely soluble in alkali,but becomes easily soluble in alkali when the acid-dissociable groupdissociates (hereinafter referred to as “acid-dissociablegroup-containing resin (B)”).

If 50% or more of the initial film thickness of a resist film remainsafter development when the resist film made only from theacid-dissociable group-containing resin (B) is developed under the samealkaline development conditions employed for forming a resist patternusing a resist film formed from a radiation-sensitive resin compositioncomprising the acid-dissociable group-containing resin (B), such acharacteristic of the acid-dissociable group-containing resin (B) isreferred to as “insoluble or scarcely soluble in alkali” in the presentinvention.

The acid-dissociable group of the acid-dissociable group-containingresin (B) refers to a group which is replaced with the hydrogen atom inan acid-functional group such as a phenolic hydroxyl group, carboxylgroup, and sulfonic group and is dissociable in the presence of an acid.

As examples of such an acid-dissociable group, a t-butoxycarbonyl group,tetrahydropyranyl group, tetrahydrofuranyl group,(thiotetrahydropyranylsulfanyl)methyl group,(thiotetrahydrofuranylsulfanyl)methyl group, alkoxy-substituted methylgroup, alkylsulfanyl-substituted methyl group, a group represented bythe following general formula (7) (hereinafter referred to as“acid-dissociable group (7)”), and the like can be given.

wherein R individually represents a linear or branched alkyl grouphaving 1-14 carbon atoms or a bridged or unbridged monovalent alicyclichydrocarbon group having 3-20 carbon atoms, or any two of R groups bondto form a bridged or unbridged divalent alicyclic hydrocarbon grouphaving 3-20 carbon atoms, with the remaining R being a linear orbranched alkyl group having 1-14 carbon atoms or a bridged or unbridgedmonovalent alicyclic hydrocarbon group having 3-20 carbon atoms, whereinall these groups are either substituted or unsubstituted.

As examples of the alkoxy-substituted methyl group, a methoxymethylgroup, ethoxymethyl group, methoxyethoxymethyl group, n-propoxymethylgroup, n-butoxymethyl group, n-pentyloxymethyl group, n-hexyloxymethylgroup, benzyloxymethyl group, and the like can be given.

As examples of the alkylsulfanyl-substituted methyl group, amethylsulfanylmethyl group, ethylsulfanylmethyl group,methoxyethylsulfanylmethyl group, n-propylsulfanylmethyl group,n-butylsulfanylmethyl group, n-pentylsulfanylmethyl group,n-hexylsulfanylmethyl group, benzylsulfanylmethyl group, and the likecan be given.

In the formula (7), as examples of the linear or branched alkyl grouphaving 1-14 carbon atoms represented by R, a methyl group, ethyl group,n-propyl group, i-propyl group, n-butyl group, 2-methylpropyl group,n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonylgroup, n-decyl group, n-undecyl group, n-dodecyl group, n-tridecylgroup, n-tetradecyl group, and the like can be given.

As the substituent for the alkyl group, one or more groups among ahydroxyl group, carboxyl group, oxo group (═O), cyano group, halogenatom (e.g., a fluorine atom, chlorine atom, etc.), linear or branchedalkoxyl group having 1-8 carbon atoms (e.g., a methoxy group, ethoxygroup, n-propoxy group, i-propoxy group, n-butoxy group, 2-methylpropoxygroup, 1-methylpropoxy group, t-butoxy group, etc.), linear or branchedalkoxyalkoxy group having 2-8 carbon atoms (e.g., a methoxymethoxygroup, ethoxymethoxy group, t-butoxymethoxy group, etc.), linear orbranched alkylcarbonyloxy group having 2-8 carbon atoms (e.g., amethylcarbonyloxy group, ethylcarbonyloxy group, t-butylcarbonyloxygroup, etc.), linear or branched alkoxycarbonyl group having 2-8 carbonatoms (e.g., a methoxycarbonyl group, ethoxycarbonyl group,t-butoxycarbonyl group, etc.), and the like can be given.

As examples of the bridged or unbridged monovalent alicyclic hydrocarbongroup having 3-20 carbon atoms represented by R, cycloalkyl groups suchas a cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexylgroup, cycloheptyl group, and cyclooctyl group; a bicyclo[2.2.1]heptylgroup, bicyclo[2.2.2]octyl group,tetracyclo[4.2.0.1^(2.5).1^(7.10)]dodecyl group, adamantyl group, andthe like can be given.

As the substituent for the above monovalent alicyclic hydrocarbon grouprepresented by R or the substituent for the above divalent alicyclichydrocarbon group formed by bonding of any two R groups, one or moregroups among a hydroxyl group, carboxyl group, oxo group (═O), cyanogroup, halogen atom (e.g., a fluorine atom, chlorine atom, etc.), linearor branched alkyl group having 1-14 carbon atoms (e.g., a methyl group,ethyl group, n-propyl group, i-propyl group, n-butyl group,2-methylpropyl group, 1-methylpropyl group, t-butyl group, etc.), linearor branched alkoxyl group having 1-8 carbon atoms (e.g., a methoxygroup, ethoxy group, n-propoxy group, i-propoxy group, n-butoxy group,2-methylpropoxy group, 1-methylpropoxy group, t-butoxy group, etc.),linear or branched alkoxyalkyl group having 2-8 carbon atoms (e.g., amethoxymethyl group, ethoxymethyl group, t-butoxymethyl group, etc.),linear or branched alkoxyalkoxy group having 2-8 carbon atoms (e.g., amethoxymethoxy group, ethoxymethoxy group, t-butoxymethoxy group, etc.),linear or branched alkylcarbonyloxy group having 2-8 carbon atoms (e.g.,a methylcarbonyloxy group, ethylcarbonyloxy group, t-butylcarbonyloxygroup, etc.), linear or branched alkoxycarbonyl group having 2-8 carbonatoms (e.g., a methoxycarbonyl group, ethoxycarbonyl group,t-butoxycarbonyl group, etc.), linear or branched cyanoalkyl grouphaving 2-14 carbon atoms (e.g., a cyanomethyl group, 2-cyanoethyl group,3-cyanopropyl group, 4-cyanobutyl, etc.), linear or branched fluoroalkylgroup having 1-14 carbon atoms (e.g., a fluoro methyl group,trifluoromethyl group, pentafluoroethyl group, etc.), and the like canbe given.

As specific preferable examples of the acid-dissociable group (7), at-butyl group and groups shown by the following formulas (7-1) to (7-20)(provided that m is an integer of 0-2) can be given.

The acid-dissociable group-containing resin (B) may contain one or moreacid-dissociable groups.

The amount of the acid-dissociable group introduced into theacid-dissociable group-containing resin (B) (the amount of the number ofacid-dissociable groups in the total number of acidic functional groupsand acid-dissociable groups in the acid-dissociable group-containingresin (B)) is preferably 5-100%, and still more preferably 10-100%,although the amount varies depending on the type of acid-dissociablegroup and the type of resin into which the acid-dissociable group isintroduced.

Various types of structure for the acid-dissociable group-containingresin (B) may be used without any restrictions as long as the aboveproperties can be obtained. Preferable structures include apoly(p-hydroxystyrene) in which part or all of the hydrogen atoms in thephenolic hydroxyl groups are replaced by acid-dissociable groups, acopolymer of p-hydroxystyrene and/or p-hydroxy-α-methylstyrene and(meth)acrylic acid in which part or all of the hydrogen atoms in thephenolic hydroxyl groups and/or carboxyl groups are replaced byacid-dissociable groups, and the like.

Also, the structure of the acid-dissociable group-containing resin (B)can be appropriately determined according to the type of radiationemployed. As an acid-dissociable group-containing resin (B) particularlypreferable for a radiation-sensitive resin composition using a KrFexcimer laser, an alkali-insoluble or scarcely alkali-soluble resinhaving a recurring unit of the following formula (8) (hereinafterreferred to as “recurring unit (8)”) and a recurring unit in which thephenolic hydroxyl group in the recurring unit (8) is protected by anacid-dissociable group can be given. This resin is hereinafter referredto as “resin (B1)”. The resin (B1) may be suitably used inradiation-sensitive resin compositions for use with other radiationssuch as ArF excimer laser, F₂ excimer laser, and electron beams.

wherein R¹⁰ individually represent a hydrogen atom or monovalent organicgroup, two or more R¹⁰s, if present, may be the same or different, and aand b each represent an integer of 1-3.

As the recurring unit (8), units wherein the non-aromatic double bond ofp-hydroxystyrene is cleaved are preferable.

The resin (B1) may further contain other recurring units.

As examples of the other recurring unit, units obtained by cleavage of apolymerizable unsaturated bond of vinyl aromatic compounds such asstyrene; (meth)acrylic esters such as t-butyl (meth)acrylate, adamantyl(meth)acrylate, and 2-methyladamantyl (meth)acrylate; and the like canbe given.

As the acid-dissociable group-containing resin (B) particularlypreferable for a radiation-sensitive resin composition using an ArFexcimer laser, an alkali-insoluble or scarcely alkali-soluble resinhaving a recurring unit of the following formula (9) (hereinafterreferred to as “recurring unit (9)”) and/or a recurring unit of thefollowing formula (10) (hereinafter referred to as “recurring unit(10)”) can be given. This resin is hereinafter referred to as “resin(B2)”. The resin (B2) may be suitably used in radiation-sensitive resincompositions for use with other radiations such as KrF excimer laser, F₂excimer laser, and electron beams.

wherein B individually represent a hydrogen atom or a monovalentacid-dissociable group, at least one of B being a monovalentacid-dissociable group, D individually represents a hydrogen atom or alinear or branched alkyl group having 1-4 carbon atoms, and k is aninteger of 0-2, or

wherein R¹¹ represents a hydrogen atom or methyl group and R¹²individually represents a linear or branched alkyl group having 1-4carbon atoms or a substituted or unsubstituted monovalent alicyclichydrocarbon group having 3-20 carbon atoms, or any two of R¹² groupsbond to form a substituted or unsubstituted, bridged or unbridged,divalent alicyclic hydrocarbon group having 3-20 carbon atoms, with theremaining R¹² group being a linear or branched alkyl group having 1-4carbon atoms or a substituted or unsubstituted monovalent alicyclichydrocarbon group having 3-20 carbon atoms.

As preferable examples of the recurring unit (10), a unit originatingfrom t-butyl (meth)acrylate and recurring units shown by the followingformulas (10-1) to (10-18) can be given.

The resin (B2) may further contain one or more types of other recurringunits.

As the other recurring units, units obtainable by cleavage of apolymerizable unsaturated bond of monomers having a norbornene skeletonsuch as, for example, norbornene(bicyclo[2.2.1]hept-2-ene),5-methylbicyclo[2.2.1]hept-2-ene, 5-ethylbicyclo[2.2.1]hept-2-ene,5-hydroxybicyclo[2.2.1]hept-2-ene, 5-fluorobicyclo[2.2.1]hept-2-ene,tetracyclo[4.4.0.1^(2.5).1^(7.10)]dodec-3-ene,8-methyltetracyclo[4.4.0.1^(2.5).1^(7.10)]dodec-3-ene,8-ethyltetracyclo[4.4.0.1^(2.5).1^(7.10)]dodec-3-ene,8-hydroxytetracyclo[4.4.0.1^(2.5).1^(7.10)]dodec-3-ene, and8-fluorotetracyclo[4.4.0.1^(2.5).1^(7.10)]dodec-3-ene; units obtainableby cleavage of a polymerizable unsaturated bond of unsaturatedcarboxylic anhydride such as maleic anhydride and itaconic anhydride;and units obtainable by cleavage of a polymerizable unsaturated bondof(meth)acrylates of the following formulas (11-1) to (11-8)(hereinafter referred to as “recurring unit (11)”) can be given:

wherein R¹³ individually represents a hydrogen atom or a methyl group,R¹⁴ individually represents a substituted or unsubstituted alkyl grouphaving 1-14 carbon atoms, a hydroxyl group, or a cyano group, i is aninteger of 0-3, and T is a methylene group or an alkylene group having2-8 carbon atoms.

The resin (B2) having the recurring unit (9) preferably further containsa recurring unit originating from maleic anhydride as the otherrecurring unit.

The resin (B2) which comprises the recurring unit (10) and the recurringunit (11) preferably further contains at least one recurring unit of thefollowing formulas (12-1) to (12-4) as the other recurring unit.

wherein R¹⁵ individually represents a hydrogen atom or a methyl group,

As the acid-dissociable group-containing resin (B) particularlypreferable for a radiation-sensitive resin composition using an F₂excimer laser, an alkali-insoluble or scarcely alkali-solublepolysiloxane having a recurring unit of the following formula (13)(hereinafter referred to as “recurring unit (13)”) and/or a recurringunit of the following formula (14) can be given. This resin ishereinafter referred to as “resin (B3)”. The resin (B3) may be suitablyused in radiation-sensitive resin compositions for use with otherradiations such as KrF excimer laser, ArF excimer laser, and electronbeams.

wherein E individually represents a monovalent organic group having anacid-dissociable group and R¹⁶ represents a substituted orunsubstituted, linear, branched, or cyclic monovalent hydrocarbon grouphaving 1-20 carbon atoms.

E in the formulas (13) and (14) is preferably a group having a structurein which the acid-dissociable group is bonded with a group having a ringskeleton.

As the group having a ring skeleton, a group having an alicyclicstructure originating from a cycloalkane having 3-8 carbon atoms,tricyclodecane, tetracyclodecane, adamantane, and the like, and a grouphaving a halogenated aromatic ring skeleton having 6-14 carbon atoms arepreferable.

As the resin (B3), a resin having the recurring unit (13) isparticularly preferable.

As specific examples of the recurring unit (13), the recurring units ofthe following formulas (13-1)-(13-4) can be given.

The resin (B3) may further contain one or more types of other recurringunits.

As preferable examples of the other recurring units, units obtained fromhydrolysis of alkyl alkoxysilanes such as methyl trimethoxysilane,methyl triethoxysilane, ethyl trimethoxysilane, and ethyltriethoxysilane, and the recurring units of the following formulas(15-1)-(15-4) can be given.

The resin (B3) can be prepared by polycondensation of a silane compoundcontaining an acid-dissociable group or by introducing anacid-dissociable group into a previously prepared polysiloxane.

When polymerizing the acid-dissociable group-containing silane compound,an acidic catalyst is preferably used as the catalyst, and afterpolycondensation of the silane compound in the presence of the acidiccatalyst, a further reaction is preferably continued in the presence ofa basic catalyst.

As examples of the acidic catalyst, inorganic acids such as hydrochloricacid, sulfuric acid, nitric acid, boric acid, phosphoric acid, titaniumtetrachloride, zinc chloride, and aluminium chloride and organic acidssuch as formic acid, acetic acid, n-propionic acid, butyric acid,valeric acid, oxalic acid, malonic acid, succinic acid, maleic acid,fumaric acid, adipic acid, phthalic acid, terephthalic acid, aceticanhydride, maleic anhydride, citric acid, benzenesulfonic acid,p-toluenesulfonic acid, and methanesulfonic acid can be given.

Of these acidic catalysts, hydrochloric acid, sulfuric acid, aceticacid, oxalic acid, malonic acid, maleic acid, fumaric acid, aceticanhydride, maleic anhydride, and the like are preferable.

These acidic catalysts may be used either individually or in combinationof two or more.

As examples of the basic catalyst, inorganic bases such as lithiumhydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide,barium hydroxide, sodium hydrogencarbonate, potassium hydrogencarbonate,sodium carbonate, and potassium carbonate and organic bases such astriethylamine, tri-n-propylamine, tri-n-butylamine, and pyridine can begiven.

These basic catalysts may be used either individually or in combinationof two or more.

When the acid-dissociable group-containing resin (B) is prepared by areaction or reactions comprising the polymerization of a polymerizableunsaturated monomer, a branched structure may be introduced into theacid-dissociable group-containing resin by a unit derived from apolyfunctional monomer having two or more polymerizable unsaturatedbonds and/or by an acetal crosslinking group. Introduction of thebranched structure improves the heat resistance of the acid-dissociablegroup-containing resin (B).

The amount of the branched structure introduced into theacid-dissociable group-containing resin (B) is preferably 10 mol % orless of the total amount of recurring units, although such an amountvaries depending on the type of branched structure and the type ofacid-dissociable group-containing resin into which the branchedstructure is introduced.

The molecular weight of the acid-dissociable group-containing resin (B)may be appropriately selected without any restrictions. Thepolystyrene-reduced weight molecular weight (hereinafter referred to as“Mw”) of the acid-dissociable group-containing resin (B) determined bygel permeation chromatography (GPC) is usually 1,000-500,000, preferably2,000-400,000, and still more preferably 3,000-300,000.

The Mw of the acid-dissociable group-containing resin (B) not having abranched structure is preferably 1,000-150,000, and particularlypreferably 3,000-100,000. The Mw of the acid-dissociablegroup-containing resin (B) having a branched structure is preferably5,000-500,000, and particularly preferably 8,000-300,000. The resistobtained from the acid-dissociable group-containing resin (B) having anMw in the above range possesses excellent development characteristics.

The ratio of Mw to the polystyrene-reduced number molecular weight(hereinafter referred to as “Mn”) determined by GPC (Mw/Mn) of theacid-dissociable group-containing resin (B) can be appropriatelyselected without any restrictions, and is usually 1-10, preferably 1-8,and particularly preferably 1-5. The resist obtained from theacid-dissociable group-containing resin (B) having a Mw/Mn in the aboverange possesses excellent resolution performance.

There are no restrictions to the method for manufacturing theacid-dissociable group-containing resin (B). As examples of the methodfor manufacturing, a method of introducing one or more acid-dissociablegroups into an acidic functional group of an alkali-soluble resin whichhas previously been manufactured, a method of polymerizing one or morepolymerizable unsaturated monomers having an acid-dissociable group,optionally together with other polymerizable unsaturated monomers, amethod of polycondensing one or more polycondensable components havingan acid-dissociable group, optionally together with otherpolycondensable components, and the like can be given.

The polymerization of the polymerizable unsaturated monomers and thepolymerization of the one or more polymerizable unsaturated monomerspossessing an acid-dissociable group in the manufacture of the alkalisoluble resin is carried out by block polymerization, solutionpolymerization, precipitation polymerization, emulsion polymerization,suspension polymerization, block-suspension polymerization, or the likeusing an appropriate polymerization initiator or catalyst such as aradical polymerization initiator, anionic polymerization catalyst,coordinated anionic polymerization catalyst, cationic polymerizationcatalyst, or the like according to the type of polymerizable unsaturatedmonomer or reaction media.

The polycondensation of the one or more polycondensable componentshaving an acid-dissociable group is preferably carried out in thepresence of an acidic catalyst using an aqueous medium or a mixture ofwater and a hydrophilic solvent.

The amount of the acid generator (A) used in the positive-toneradiation-sensitive resin composition of the present invention can beappropriately selected depending on the desired properties of theresist. The acid generator (A) is preferably used in an amount of0.001-70 parts by weight, more preferably 0.01-50 parts by weight, andparticularly preferably 0.1-20 parts by weight for 100 parts by weightof the acid-dissociable group-containing resin (B). Using the acidgenerator (A) in an amount of 0.001 parts by weight or more preventsdeterioration of the sensitivity and resolution of the resist. Also,using the acid generator (A) in an amount of 70 parts by weight or lessprevents deterioration of the applicability and pattern shape of theresist.

Acid Diffusion Controller

An acid diffusion controller is preferably added to the positive-toneradiation-sensitive resin composition of the present invention. The aciddiffusion controller controls diffusion of an acid generated from theacid generator (A) upon exposure in the resist film and preventsunfavorable chemical reactions in the unexposed region. Addition of theacid diffusion controller further improves storage stability of theresulting radiation-sensitive resin composition and resolution of theresist. Moreover, addition of the acid diffusion controller prevents theline width of the resist pattern from changing due to changes in thepost-exposure delay (PED) between exposure and development, whereby aradiation-sensitive resin composition with remarkably superior processstability can be obtained.

As the acid diffusion controller, nitrogen-containing organic compoundsof which the basicity does not change due to exposure or heat treatmentduring formation of a resist pattern are preferable.

As the above-mentioned nitrogen-containing organic compound, a compoundof the following formula (16) (hereinafter called “nitrogen-containingcompounds (i)”), a diamino compound having two nitrogen atoms in themolecule (hereinafter called “nitrogen-containing compounds (ii)”), apolyamino compound having three or more nitrogen atoms (hereinaftercalled “nitrogen-containing compounds (iii)”), a compound containing anamide group, a urea compound, a heterocyclic compound containing anitrogen atom, and the like can be given.

wherein R¹⁷ individually represents a hydrogen atom, alkyl group, arylgroup, or aralkyl group which may be substituted or unsubstituted.

As the substituted or unsubstituted alkyl group in the above formula(16), groups having 1-15 carbon atoms and preferably 1-10 carbon atoms,such as a methyl group, ethyl group, n-propyl group, i-propyl group,n-butyl group, i-butyl group, sec-butyl group, t-butyl group, n-pentylgroup, neopentyl group, n-hexyl group, thexyl group, n-heptyl group,n-octyl group, n-ethylhexyl group, n-nonyl group, n-decyl group, and thelike can be given.

As examples of the substituted or unsubstituted aryl group, the grouphaving 6-12 carbon atoms such as a phenyl group, tolyl group, xylylgroup, cumenyl group, and 1-naphthyl group can be given.

As examples of the substituted or unsubstituted aralkyl group, the grouphaving 7-19 carbon atoms and preferably 7-13 carbon atoms such as abenzyl group, α-methylbenzyl group, phenethyl group, and1-naphthylmethyl group can be given.

As examples of the nitrogen-containing compounds (i), monoalkylaminessuch as n-hexylamine, n-heptylamine, n-octylamine, n-nonylamine, andn-decylamine; dialkylamines such as di-n-butylamine, di-n-pentylamine,di-n-hexylamine, di-n-heptylamine, di-n-octylamine, di-n-nonylamine, anddi-n-decylamine; trialkylamines such as triethylamine,tri-n-propylamine, tri-n-butylamine, tri-n-pentylamine,tri-n-hexylamine, tri-n-heptylamine, tri-n-octylamine, tri-n-nonylamine,and tri-n-decylamine; aromatic amines such as aniline, N-methylaniline,N,N-dimethylaniline, 2-methylaniline, 3-methylaniline, 4-methylaniline,4-nitroaniline, diphenylamine, triphenylamine, and 1-naphthylamine; andalkanolamines such as ethanolamine, diethanolamine, and triethanolaminecan be given.

As examples of the nitrogen-containing compounds (ii), ethylenediamine,N,N,N′,N′-tetramethylethylenediamine, tetramethylenediamine,hexamethylenediamine, N,N,N′,N′-tetrakis(2-hydroxyethyl)ethylenediamine,N,N,N′,N′-tetrakis(2-hydroxypropyl)ethylenediamine,4,4′-diaminodiphenylmethane, 4,4′-diamino diphenyl ether,4,4′-diaminobenzophenone, 4,4′-diaminodiphenylamine,2,2′-bis(4-aminophenyl)propane,2-(3-aminophenyl)-2-(4-aminophenyl)propane,2-(4-aminophenyl)-2-(3-hydroxyphenyl)propane,2-(4-aminophenyl)-2-(4-hydroxyphenyl)propane,1,4-bis[1-(4-aminophenyl)-1-methylethyl]benzene,1,3-bis[1-(4-aminophenyl)-1-methylethyl]benzene, and the like can begiven.

As examples of the nitrogen-containing compound (iii),polyethyleneimine, polyallylamine, a polymer ofdimethylaminoethylacrylamide, and the like can be given.

Examples of compounds containing an amide group include formamide,N-methylformamide, N,N-dimethylformamide, acetamide, N-methylacetamide,N,N-dimethylacetamide, propionamide, benzamide, pyrrolidone, andN-methylpyrrolidone.

Examples of urea compounds include urea, methylurea, 1,1-dimethylurea,1,3-dimethylurea, 1,1,3,3-tetramethylurea, 1,3-diphenylurea, andtributylthiourea.

As examples of the nitrogen-containing heterocyclic compound, imidazolessuch as imidazole, benzimidazole, 2-methylimidazole, 4-methylimidazole,1,2-dimethylimidazole, 2-phenylimidazole, 4-phenylimidazole,4-methyl-2-phenylimidazole, and 2-phenylbenzimidazole; pyridines such aspyridine, 2-methylpyridine, 4-methylpyridine, 2-ethylpyridine,4-ethylpyridine, 2-phenylpyridine, 4-phenylpyridine,N-methyl-4-phenylpyridine, nicotine, nicotinic acid, nicotinamide,quinoline, 8-oxyquinoline, and acridine; pyrazine, pyrazole, pyridazine,quinoxaline, purine, pyrrolidine, piperidine, 1-piperidine ethanol,2-piperidine ethanol, morpholine, 4-methylmorpholine, piperazine,1,4-dimethylpiperazine, 1,4-diazabicyclo[2.2.2]octane, and the like canbe given.

A compound having an acid-dissociable group can also be used as thenitrogen-containing organic compound.

As examples of the nitrogen-containing organic compound having anacid-dissociable group, N-(t-butoxycarbonyl)piperidine,N-(t-butoxycarbonyl)imidazole, N-(t-butoxycarbonyl)benzimidazole,N-(t-butoxycarbonyl)-2-phenylbenzimidazole,N-(t-butoxycarbonyl)di-n-octylamine, N-(t-butoxycarbonyl)diethanolamine,N-(t-butoxycarbonyl)dicyclohexylamine, andN-(t-butoxycarbonyl)diphenylamine can be given.

Of these nitrogen-containing organic compounds, the nitrogen-containingcompounds (i), nitrogen-containing compounds (ii), nitrogen-containingheterocyclic compounds, and nitrogen-containing organic compounds havingan acid-dissociable group are preferable. The acid diffusion controllersmay be used either individually or in combination of two or more.

The amount of the acid diffusion controller to be added is preferably 15parts by weight or less, more preferably 0.001-10 parts by weight, andparticularly preferably 0.005-5 parts by weight for 100 parts by weightof the acid-dissociable group-containing resin (B). Incorporating theacid diffusion controller in an amount of 0.001 parts by weight or moreprevents deterioration of the pattern shape and size fidelity as aresist. Also, incorporating the acid diffusion controller in an amountof 15 parts by weight or less improves the sensitivity as a resist andimproves the developability of the exposure area.

Dissolution Controller

A dissolution controller that improves the solubility in an alkalinedeveloper by the action of an acid may be added to the positive-toneradiation sensitive resin composition of the present invention.

As examples of such a dissolution controller, compounds having an acidfunctional group such as a phenolic hydroxyl group, carboxyl group, andsulfonic group, compounds in which the hydrogen atom in the acidicfunctional group is replaced by an acid-dissociable group, and the likecan be given.

These dissolution controllers may be used either individually or incombination of two or more. The proportion of the dissolutioncontrollers to be added is 20 parts by weight or less, and preferably 10parts by weight or less for 100 parts by weight of the total resincomponent in the radiation-sensitive resin composition.

Surfactant

A surfactant that improves applicability, striation, developability, andthe like may be added to the positive-tone radiation sensitive resincomposition of the present invention.

As the surfactants, any of anionic surfactants, cationic surfactants,nonionic surfactants, and ampholytic surfactants may be used. Of these,nonionic surfactants are preferable.

As examples of nonionic-type surfactants, polyoxyethylene higher alkylethers, polyoxyethylene higher alkyl phenyl ethers, higher fatty aciddiesters of polyethylene glycol, commercially available products such asKP (manufactured by Shin-Etsu Chemical Co., Ltd.), Polyflow(manufactured by Kyoeisha Chemical Co., Ltd.), EFTOP (manufactured byTohkem Products Corporation), MEGAFAC (manufactured by Dainippon Ink andChemicals, Inc.), Fluorad (manufactured by Sumitomo 3M, Ltd.), AsahiGuard, Surflon (manufactured by Asahi Glass Co., Ltd.), and the like canbe given.

These surfactants may be used either individually or in combination oftwo or more.

The proportion of the surfactants to be added is 2 parts by weight orless, and preferably 1.5 parts by weight or less, as an effectivecomponent, for 100 parts by weight of the total resin components in theradiation-sensitive resin composition.

Photosensitizer

A photosensitizer which absorbs radiation energy and transmits theenergy to the acid generator (A), thereby increasing the amount of anacid generated upon exposure and further improving the sensitivity maybe added to the positive-tone radiation sensitive resin composition ofthe present invention.

As examples of preferable sensitizers, acetophenones, benzophenones,naphthalenes, biacetyl, eosine, rose bengale, pyrenes, anthracenes,phenothiazines, and the like can be given.

These sensitizers may be used either individually or in combinations oftwo or more. The proportion of the sensitizers to be added is 50 partsby weight or less, and preferably 30 parts by weight or less for 100parts by weight of the total resin component in the radiation-sensitiveresin composition.

Other Additives

Other additives may be added to the positive-tone radiation sensitiveresin composition of the present invention, as required, to the extentthat does not impair the effects of the present invention. Examples ofsuch additives include dyes, pigments, adhesion adjuvants, halationinhibitors, preservatives, defoaming agents, and shape improvers.Specific additives include 4-hydroxy-4′-methylchalcone, and the like.

Addition of a dye or a pigment adjusts transmittance of theradiation-sensitive resin composition, thereby decreasing the effects ofhalation during exposure. Use of an adhesion improver improves adhesionto the substrates.

Preparation of Composition Solution

The positive-tone radiation-sensitive resin composition of the presentinvention is usually prepared as a composition solution by dissolvingthe components in a solvent to obtain a homogeneous solution and,optionally, filtering the solution through a filter with a pore size ofabout 0.2 μm.

Ethers, esters, ether esters, ketones, ketone esters, amides, amideesters, lactams, lactones, and (halogenated) hydrocarbons are given asexamples of the solvent which can be used here. Specific examples areethylene glycol monoalkyl ethers, diethylene glycol dialkyl ethers,propylene glycol monoalkyl ethers, propylene glycol dialkyl ethers,ethylene glycol monoalkyl ether acetates, propylene glycol monoalkylether acetates, acetates, hydroxy acetates, lactates, alkoxy acetates,(non)cyclic ketones, acetoacetates, pyruvates, propionates, N,N-dialkylformamides, N,N-dialkyl acetamides, N-alkylpyrolidones, γ-lactones,(halogenated) aliphatic hydrocarbons, and (halogenated) aromatichydrocarbons.

More specifically, such solvents include ethylene glycol monomethylether, ethylene glycol monoethyl ether, ethylene glycol mono-n-propylether, ethylene glycol mono-n-butyl ether, diethylene glycol dimethylether, diethylene glycol diethyl ether, diethylene glycol di-n-propylether, diethylene glycol di-n-butyl ether, ethylene glycol monomethylether acetate, ethylene glycol monoethyl ether acetate, propylene glycolmonomethyl ether acetate, propylene glycol monoethyl ether acetate,propylene glycol mono-n-propyl ether acetate, isopropenyl acetate,isopropenyl propionate, toluene, xylene, methyl ethyl ketone,cyclohexanone, 2-heptanone, 3-heptanone, 4-heptanone, ethyl2-hydroxypropionate, ethyl 2-hydroxy-2-methyl propionate, ethylethoxyacetate, ethyl hydroxyacetate, methyl 2-hydroxy-3-methylbutyrate,methyl lactate, ethyl lactate, n-propyl lactate, i-propyl lactate,3-methoxybutyl acetate, 3-methyl-3-methoxybutyl acetate,3-methyl-3-methoxybutyl propionate, 3-methyl-3-methoxybutyl butyrate,ethyl acetate, n-propyl acetate, n-butyl acetate, methyl acetoacetate,ethyl acetoacetate, methyl 3-methoxy propionate, ethyl3-methoxypropionate, methyl 3-ethoxypropionate, ethyl3-ethoxypropionate, N-methyl pyrolidone, N,N-dimethyl formamide, andN,N-dimethyl acetamide.

Of these solvents, propylene glycol monoalkyl ether acetates,2-heptanone, lactates, 2-hydroxypropionates, 3-alkoxypropionates, andthe like are desirable to ensure excellent uniformity of the filmsurface during application.

These solvents may be used either individually or in combination of twoor more.

One or more solvents with a high boiling point may optionally be addedto the solvent. Examples of such solvents with a high boiling pointinclude benzyl ethyl ether, di-n-hexyl ether, diethylene glycolmonomethyl ether, diethylene glycol monoethyl ether, acetonylacetone,isophorone, caproic acid, caprylic acid, 1-octanol, 1-nonanol, benzylalcohol, benzyl acetate, ethyl benzoate, diethyl oxalate, diethylmaleate, γ-butyrolactone, ethylene carbonate, propylene carbonate, andethylene glycol monophenyl ether acetate.

These other solvents may be used either individually or in combinationof two or more.

The proportion of the other solvents to be added is 50 wt % or less, andpreferably 30 wt % or less of the total amount of solvents used.

The solvents are used in a total amount to make the total solid contentof the solution composition usually 5-50 wt %, preferably 10-50 wt %,more preferably 10-40 wt %, and particular preferably 10-30 wt %. Anoptimal amount is 10-25 wt %. The total solid content in the aboveranges is desirable to ensure excellent uniformity of the film surfaceduring application.

Formation of Resist Pattern

A resist pattern is formed from the positive-tone radiation-sensitiveresin composition of the present invention by applying the compositionsolution thus prepared to, for example, substrates such as a siliconwafer or a wafer coated with aluminum using an appropriate applicationmethod such as rotational coating, cast coating, and roll coating toform a resist film. Then, after optional heat treatment (hereinafterreferred to as “PB”), the resist film is exposed to radiation through amask with a prescribed pattern.

As radiation that can be used here, deep ultraviolet rays such as abright line spectrum of a mercury lamp (wavelength: 254 nm), KrF excimerlaser (wavelength: 248 nm), ArF excimer laser (wavelength: 193 nm), F₂excimer laser (wavelength: 157 nm), and EUV (wavelength: 13 nm); X-rayssuch as synchrotron radiation, charged particle rays such as electronbeams, and the like can be used according to the types of acidgenerators (A). Preferable radiations are deep ultraviolet rays andcharged particle rays, with particularly preferable radiations being aKrF excimer laser (wavelength: 248 nm), ArF excimer laser (wavelength:193 nm), and electron beams.

The exposure conditions such as the dose of radiation are appropriatelydetermined according to the composition of the positive-toneradiation-sensitive resin composition, types of additives, and the like.

When forming a resist pattern, post exposure bake (hereinafter called“PEB”) which is a heat treatment after exposure is preferable toincrease apparent sensitivity of the resist.

PEB is performed at a temperature of 30-200° C., and preferably 50-150°C., although the temperature varies depending on the composition of theradiation-sensitive resin composition, types of additives, and the like.

The resist film after exposure is developed in an alkaline developer toform a predetermined resist pattern.

As the alkaline developer, an alkaline aqueous solution in which one ormore alkaline compounds such as an alkaline metal hydroxide, aqueousammonia, alkylamines, alkanolamines, heterocyclic amines,tetraalkylammonium hydroxides, choline,1,8-diazabicyclo[5.4.0]-7-undecene, and 1,5-diazabicyclo[4.3.0]-5-noneneare dissolved is used. An aqueous solution of tetraalkylammoniumhydroxide is a particularly preferable alkaline developer.

The concentration of the alkaline aqueous solution is preferably 10 wt %or less, more preferably 1-10 wt %, and particularly preferably 2-5 wt%. The concentration of the alkaline aqueous solution less than 10 wt %prevents dissolution of an unexposed area in the developer.

The addition of an appropriate amount of a surfactant to the alkalinedeveloper is desirable to increase wettability of the resist to thedeveloper.

The resist film is generally washed with water after development usingthe alkaline developer.

EXAMPLES

The embodiments of the present invention are described in more detail byexamples. However, these examples should not be construed as limitingthe present invention.

Synthesis of Sulfonium Salt Compound (1)

Example 1

20 g of 2-naphthalene thiol was dissolved in 100 ml of acetone, and13.39 g of 4-chloro-1-butanol and 25.04 g of triethylamine were addeddropwise. The mixture was reacted for 12 hours at room temperature whilestirring and poured into 100 ml of water. The reaction mixture wasextracted three times with 50 ml of ethyl acetate. The resulting organiclayer was washed three times with 50 ml of 10 wt % sodium carbonateaqueous solution and three times with 50 ml of 5 wt % oxalic-acidaqueous solution. The separated water layer was repeatedly washed withdistilled water until pH 7. The organic layer was dried using 3 g ofmagnesium sulfate. After removing magnesium sulfate by filtration, thesolvent was evaporated using a rotary evaporator to obtain 20.2 g of4-(naphthalen-2-ylsulfanyl)butan-1-ol as a highly viscous oily liquid.

Next, 20.2 g of the 4-(naphthalen-2-ylsulfanyl)butan-1-ol was dissolvedin 120 ml of dichloromethane and 17.3 g of triethylamine was added tothe solution. After cooling in an ice water bath at 0° C., 11.78 g ofmethanesulfonyl chloride was added dropwise over five minutes. Themixture was reacted for 15 minutes in an ice water bath and poured into100 ml of ice water. The organic layer was washed two times with 70 mlof 10 wt % sodium hydrogen carbonate aqueous solution and three timeswith 5 wt % oxalic-acid aqueous solution. The separated water layer wasrepeatedly washed with distilled water until pH 7. The organic layer wasdried using 5 g of magnesium sulfate. After removing magnesium sulfateby filtration, the solvent was evaporated using a rotary evaporator toobtain 22.0 g of 4-[(naphthalen-2-yl)sulfanyl]butyl ester ofmethansulfonic acid as a colorless liquid.

22.0 g of the 4-[(naphthalen-2-yl)sulfanyl]butyl ester of methansulfonicacid was dissolved in 100 ml of acetonitrile and the mixture was reactedfor 14 hours while heating over a hot water bath at 70° C. The reactionmixture was powered into 100 ml of water, acetonitrile was evaporatedusing a rotary evaporator, and the residue was washed three times with30 ml of diethyl ether to obtain 100 g of an aqueous solution of1-(naphthalen-2-yl)tetrahydrothiophenium methane sulfonate. 40 g of apreviously prepared 30 wt % aqueous solution of ammoniumnonafluoro-n-butane sulfonate was added dropwise to the resultingaqueous solution. The precipitate was collected by filtration and driedunder vacuum to obtain 28.6 g of1-(naphthalen-2-yl)tetrahydrothiophenium nonafluoro-n-butane sulfonate.

The structure of this compound was identified using fast atombombardment (FAB) mass spectrometry and ¹H-NM analysis. FIG. 1 shows the¹H-NMR spectrum of this compound. The compound is herein indicated as“sulfonium salt (A-1)”.

Example 2

9 g of dichloromethane and 1.0 g of sodium2-(bicyclo[2.2.1]heptan-2-yl)-1,1,2,2-tetrafluoroethane sulfonate wereadded to 10 g of an aqueous solution of1-(naphthalen-2-yl)tetrahydrothiopheniummethane sulfonate which wassynthesized in the same manner as the sulfonium salt (A-1). The mixturewas reacted while vigorously stirring for 12 hours using a magneticstirrer. After the reaction, 10 g of dichloromethane was added. Theorganic layer was washed five times with 10 g of water and dried using 2g of magnesium sulfate. The magnesium sulfate was then removed byfiltration. The solvent was evaporated using a rotary evaporator toobtain 1.4 g of 1-(naphthalen-2-yl)tetrahydrothiophenium2-(bicyclo[2.2.1]heptan-2-yl)-1,1,2,2-tetrafluoroethane sulfonate as awhite solid.

The structure of this compound was identified using fast atombombardment (FAB) mass spectrometry and ¹H-NMR analysis. FIG. 2 showsthe ¹H-NMR spectrum of this compound. The compound is herein indicatedas “sulfonium salt (A-2)”.

Example 3

6.0 g of 1-(naphthalen-2-yl)tetrahydrothiophenium methane sulfonatesynthesized in the same manner as in Example 1 was added dropwise to 5.0g of previously prepared 30 wt % methanol solution of perfluoro-n-octanesulfonic acid. After the addition, the reaction solution was poured into50 g of water. White precipitate was collected by filtration, washedseveral times with water, and dried under vacuum to obtain 2.1 g of1-(naphthalen-2-yl)tetrahydrothiophenium perfluoro-n-octane sulfonate asa white solid.

The structure of this compound was identified using fast atombombardment (FAB) mass spectrometry and ¹H-NMR analysis. FIG. 3 showsthe ¹H-NMR spectrum of this compound. The compound is herein indicatedas “sulfonium salt (A-3)”.

Example 4

The method described in Japanese Patent Application Laid-open No.2002-229192 was followed using 5-norbornen-2-endo-3-endo-dimethanol as astarting material to obtain 4.5 g of corresponding norbornanedimethylenesulfoxide.

4.5 g of the norbornanedimethylene sulfoxide was placed in a 500 mleggplant flask and dissolved in 100 ml of tetrahydrofuran. The solutionwas cooled in a dry-ice acetone bath at −78° C. and 5.4 ml oftrimethylsilyltrifluoromethane sulfonate was added, followed bycontinued stirring for one hour. Stirring was continued for a further1.5 hours at a bath temperature of −40° C. After decreasing the bathtemperature to −78° C., 100 ml of a previously prepared solution of 0.5mol of 2-naphthyl magnesium bromide in 1 l of tetrahydrofuran was addeddropwise. The mixture was stirred at the same temperature for one hour.The reaction solution was poured into 500 ml of 5 wt % aqueous solutionof trifluoromethansulfonic acid and tetrahydrofuran was evaporated usinga rotary evaporator. 100 ml of chloroform was added to the residue toextract a reaction product. The chloroform layer was washed three timeswith 100 ml of 5 wt % aqueous solution of trifluoromethansulfonic acidand dried using anhydrous magnesium sulfate, which was then removed byfiltration. Chloroform was evaporated using a rotary evaporator, theresidue was dried under reduced pressure, and purified by columnchromatography (developing solvent: dichloromethane) to obtain 4.1 g ofa salt of trifluoromethane sulfonate having a cation moiety of thefollowing formula (17).

4.1 g of the trifluoromethane sulfonate salt was replaced with chloridesalt using 60 g of anion exchange column (A25) to which the chlorineanion was adsorbed with ammonium chloride. The chloride salt wasdissolved in 50 ml of water and reacted with 45 ml of 30 wt % ammoniumnonafluoro-n-butane sulfonate aqueous solution, which was previouslyprepared from nonafluoro-n-butane sulfonic acid and ammonia. Theresulting precipitate was collected by filtration and dried to obtain4.4 g of nonafluoro-n-butanesulfonate having a cation moiety of theformula (17).

The structure of this compound was identified using fast atombombardment (FAB) mass spectrometry and ¹H-NMR analysis. FIG. 4 showsthe ¹H-NMR spectrum of this compound. The compound is herein indicatedas “sulfonium salt (A-4)”.

Example 5

9.464 g of tetramethylene sulfoxide was dissolved in 200 ml ofdichloromethane. After cooling the solution to −78° C., 16.7 g ofbromotrimethyl silane was added dropwise. The mixture was then heated to−50° C. and stirred for one hour. After cooling the resulting solutionto −78° C., a tetrahydrofuran solution of 6-n-butoxy-2-naphthylmagnesium bromide prepared from 38 g of 2-bromo-6-n-butoxy naphthalene,3.65 g of magnesium, and 263 ml of tetrahydrofuran according to themethod described in J. Am. Chem. Soc., Vol. 118, P. 6841-6852 (1996) wasadded dropwise over one hour. After increasing the reaction temperatureto −50° C., the mixture was reacted for one hour. Then, 750 ml of 10 wt% hydrobromic acid aqueous solution was added to terminate the reaction.The organic solvent was evaporated using a rotary evaporator. Insolublecomponents were extracted three times with 200 ml of diethyl ether and100 ml of 30 wt % ammonium nonafluoro-n-butane sulfonate aqueoussolution was added dropwise to the water layer while stirring. Theresulting precipitate was filtered, washed with distilled water, anddried using a vacuum pump to obtain 10.4 g of1-(6-n-butoxynaphthalen-2-yl)tetrahydrothiophenium nonafluoro-n-butanesulfonate as a white solid.

The structure of this compound was identified using fast atombombardment (FAB) mass spectrometry and ¹H-NMR analysis. FIG. 5 showsthe ¹H-NMR spectrum of this compound. The compound is herein indicatedas “sulfonium salt (A-5)”.

Example 6

30 g 6-n-butoxy-2-naphthalene thiol was obtained by the method ofnon-patent document 5 from 72 g of 2-bromo-6-n-butoxy naphthaleneprepared according to the method described in J. Am. Chem. Soc., Vol.118, P. 6841-6852 (1996) and 6-n-butoxy-2-naphthyl magnesium bromideprepared from 7.5 g of magnesium. Next, 30 g of 6-n-butoxy-2-naphthalenethiol was dissolved in 150 ml of acetone and 14.0 g of4-chloro-1-butanol was added to the solution. After the addition of 26.1g of triethylamine dropwise over 15 minutes, the mixture was reacted for15 hours at room temperature while stirring. Next, 150 ml of ethylacetate and 150 ml of water were added to the reaction mixture. Afterremoving the water layer using a separating funnel, the organic layerwas washed three times with 75 ml of a 10 wt % sodium carbonate aqueoussolution, then repeatedly washed with 5 wt % oxalic acid aqueoussolution until the water layer becomes pH 2. Then, the organic layer waswashed with purified water until the water layer becomes pH 7 and driedusing magnesium sulfate. After drying, magnesium sulfate was removed byfiltration and the solvent was evaporated using a rotary evaporator at40° C. under reduced pressure by a stream aspirator to obtain 29.4 g of4-hydroxybutyl-(6-n-butoxynaphthalen-2-yl)sulfide, of which the puritydetermined by high performance liquid chromatography (HPLC) was 95 wt %or more.

29.4 g of 4-hydroxybutyl-(6-n-butoxynaphthalen-2-yl)sulfide thusobtained was dissolved in 180 ml of dichloromethane. After cooling to−5° C. over an ice saturated brine bath, 13.3 g of methanesulfonylchloride was added. Then, 19.6 g triethylamine was added dropwise over15 minutes while controlling the temperature at less than 0° C. Afterreacting for one hour at 0-5° C., 100 ml of ice water was added and theresulting mixture was stirred for five minutes. The water layer wasremoved using a separating funnel. The organic layer was washed twicewith 70 ml of 10 wt % sodium hydrogencarbonate aqueous solution andthree times with 70 ml of 5 wt % oxalic acid aqueous solution. Then, theorganic layer was washed with purified water until the water layerbecomes pH 7 and dried using magnesium sulfate. After drying, magnesiumsulfate was removed by filtration and the solvent was evaporated using arotary evaporator at room temperature under reduced pressure by a streamaspirator to obtain 33 g of crude product of4-methanesulfonyloxybutyl-(6-n-butoxynaphthalen-2-yl)sulfide, of whichthe purity determined by HPLC was 93 wt %. The crude product contained 5wt % of 1-(6-n-butoxynaphthalen-2-yl)tetrahydrothiophenium methanesulfonate.

33 g of crude product of4-methanesulfonyloxybutyl-(6-n-butoxynaphthalen-2-yl)sulfide thusobtained was mixed with 150 g of acetonitrile. After heating to 70° C.over an oil bath, the mixture was reacted for 14 hours with stirring.The reaction mixture was poured into 100 g of water and acetonitrile wasevaporated using a rotary evaporator at 40° C. under reduced pressure bya stream aspirator. The residue was extracted three times with 50 ml ofdiethyl ether to remove water-insoluble components, thereby obtaining anaqueous solution of 1-(6-n-butoxynaphthalen-2-yl)tetrahydrothiopheniummethane sulfonate, of which the purity determined by HPLC was 98 wt % ormore.

100 ml of dichloromethane and 28.61 g of sodium2-(bicyclo[2.2.1]heptan-2-yl)tetrafluoroethane sulfonate were added tothe aqueous solution of1-(6-n-butoxynaphthalen-2-yl)tetrahydrothiophenium methane sulfonate andthe mixture was stirred for 12 hours. After removing the water layerusing a separating funnel, the organic layer was washed five times with40 ml of purified water. The solvent was evaporated using a rotaryevaporator under reduced pressure by a stream aspirator at roomtemperature and the residue was dried at 50° C. under reduced pressureto obtain 24.2 g of 1-(6-n-butoxynaphthalen-2-yl)tetrahydrothiophenium2-(bicyclo[2.2.1]heptan-2-yl)tetrafluoroethane sulfonate as a whitesolid.

The structure of this compound was identified using fast atombombardment (FAB) mass spectrometry, ¹H-NMR analysis, and ¹⁹F-NMRanalysis. FIG. 6 shows the ¹H-NMR spectrum of this compound. Thecompound is herein indicated as “sulfonium salt (A-6)”.

(Measurement of Molar Extinction Coefficient)

Sulfonium salts (A-1) to (A-5) were dissolved in acetonitrile to preparesolutions with a concentration of 5.0×10⁻⁴ mmol/liter. Absorptionspectra of these solutions were measured using a quartz cell with anexposure length of 10 mm by an ultraviolet-visible regionspectrophotometer (V550 manufactured by Jasco Corp.).

Absorption spectra of the following sulfonium salts (a-1) to (a-3) werealso measured in the same manner.

The molar extinction coefficient of each sulfonium salt at a wavelengthof 193 nm was calculated from the resulting absorption spectrum. Theresults are shown in Table 1.

-   Sulfonium salt (a-1):    1-(4-fluoronaphthalen-1-yl)tetrahydrothiophenium nonafluoro-n-butane    sulfonate-   Sulfonium salt (a-2):    1-(4-n-butoxynaphthalen-1-yl)tetrahydrothiophenium    nonafluoro-n-butane sulfonate-   Sulfonium salt (a-3): Triphenylsulfonium    nonafluoro-n-butanesulfonate

TABLE 1 Molar extinction coefficient at a wavelength of 193 nm Sulfoniumsalt (I/mol · cm) A-1 10,600 A-2 10,650 A-3 10,620 A-4 8,990 A-5 7,900A-6 7,920 a-1 14,120 a-2 21,540 a-3 26,600

As is clear from Table 1, the sulfonium salt compounds (I) of thepresent invention were confirmed to have small absorption at awavelength of 193 nm and high transparency to an ArF excimer laser ascompared with conventional sulfonium salt compounds.

Examples 7-18 and Comparative Example 1

(Performance Evaluation of Positive-tone Radiation Sensitive ResinComposition)

Components shown in Table 2 (part(s) indicates part(s) by weight) weremixed to prepare homogeneous solutions. The solutions were filteredthrough a membrane filter with a pore diameter of 0.2 μm to preparesolution compositions.

Each composition solution was applied to a silicon wafer, coated with anantireflection film (ARC) as a lower layer membrane, by spin coating toobtain a resist film with a thickness of 0.34 μm, followed by baking(PB) on a hot plate at 130° C. for 90 seconds. The resist film wasexposed to an ArF excimer laser using an apparatus manufactured by NikonCorp. (numerical aperture 0.55), baked (PEB) on a hot plate at 130° C.for 90 seconds, developed in a 2.38 wt % aqueous solution oftetramethylammonium hydroxide for one minute, washed with water, anddried to form a resist pattern.

The resist film performance was evaluated on the following itemsaccording to the methods described below. The evaluation results areshown in Table 3.

-   Sensitivity: An optimum dose capable of forming a 1:1 line width    from a line-and-space (1L1S) pattern with a line width of 0.15 μm    was taken as sensitivity.-   Resolution: The minimum line and space (1L1S) dimension resolved by    an optimum dose of irradiation was taken as the resolution.-   Pattern shape: The cross-section of a line-and-space (1L1S) pattern    with a line width of 0.15 μm was measured by a scanning electron    microscope.-   LER: A resist pattern was formed by irradiating a sample with light    at a dose reproducing a line and space pattern (1L1S) with a line    width of0.15 μm. The surface of one side of the pattern edge was    inspected at two or more positions using a scanning electron    microscope (SEM) to calculate 3σ dispersion in the direction    perpendicular to the direction of the pattern lines. The LER was    evaluated according to the following standard.

◯: 3σ dispersion is less than 8 nm.

Δ: 3σ dispersion is 8 nm or more, but less than 10 nm.

×: 3σ dispersion is 10 nm or more.

-   Storage stability: Each composition solution was stored at 20° C.    for three months to measure sensitivity immediately after    preparation, after one month of storage, and after three months of    storage. The storage stability was evaluated according to the    following standard.

◯: Sensitivity change after three months of storage is less than 3%.

×: Sensitivity change after three months of storage is 3% or more.

The components in Table 2 other than those described above are asfollows.

(B) Acid-dissociable Group-containing Resin

-   -   B-1: Copolymer in which the ratio of the recurring unit of the        formula (10-15) (R¹¹=methyl group, hereinafter the same) and the        recurring unit of the formula (11-1) (R¹³=methyl group,        hereinafter the same) is 40:60 (Mw=9,000)    -   B-2: Copolymer in which the ratio of the recurring unit of the        formula (10-15), the recurring unit of the formula (11-1), and        the recurring unit of the formula (12-1) (R¹⁵=methyl group,        hereinafter the same) is 45:30:25 (Mw=9,000)    -   B-3: Copolymer in which the ratio of the recurring unit of the        formula (10-17) (R¹¹=methyl group, hereinafter the same) and the        recurring unit of the formula (11-1) is 40:60 (Mw=6,000)    -   B-4: Copolymer in which the ratio of the recurring unit of the        formula (10-17), the recurring unit of the formula (11-1), and        the recurring unit of the formula (12-1) is 45:30:25 (Mw=7,000)        Photoacid Generator    -   A-1: Sulfonium salt (A-1).    -   A-2: Sulfonium salt (A-2).    -   A-3: Sulfonium salt (A-3).    -   A-4: Sulfonium salt (A-4).    -   A-5: Sulfonium salt (A-5).    -   A-6: Sulfonium salt (A-6).    -   a-1: 1-(2-oxo-n-butyl)tetrahydrothiophenium        nonafluoro-n-butanesulfonate        Acid Diffusion Controller    -   C-1: 2-Phenylbenzimidazole    -   C-2: N-t-butoxycarbonyl-2-phenylbenzimidazole        Dissolution Controller    -   D-1: t-Butyl deoxycholate        Solvent    -   S-1: Propylene glycol monomethyl ether acetate    -   S-2: γ-Butyrolactone

TABLE 2 Acid-dissociable Photoacid group-containing Acid diffusionDissolution generator resin (B) controller controller Solvent (part byweight) (part by weight) (part by weight) (part by weight) (part byweight) Example 7 A-1 (5) B-1 (100) C-1 (0.25) S-1 (700) S-2 (35)Example 8 A-1 (5) B-2 (100) C-1 (0.25) S-1 (700) S-2 (35) Example 9 A-1(5) B-3 (100) C-1 (0.25) S-1 (700) S-2 (35) Example 10 A-1 (5) B-4 (100)C-1 (0.25) S-1 (700) S-2 (35) Example 11 A-2 (5) B-2 (100) C-1 (0.25)S-1 (700) S-2 (35) Example 12 A-3 (5) B-2 (100) C-1 (0.25) S-1 (700) S-2(35) Example 13 A-1 (5) B-1 (90) C-2 (0.25) D-1 (10) S-1 (700) S-2 (35)Example 14 A-1 (8) B-2 (100) C-1 (0.40) S-1 (700) S-2 (35) Example 15A-1 (8) B-2 (100) C-1 (0.40) S-1 (700) S-2 (35) Example 16 A-5 (8) B-2(100) C-1 (0.40) S-1 (700) S-2 (35) Example 17 A-4 (5) B-2 (100) C-1(0.25) S-1 (700) S-2 (35) Example 18 A-6 (8) B-2 (100) C-1 (0.40) S-1(700) S-2 (35) Comparative a-1 (8) B-2 (100) C-1 (0.25) S-1 (700)Example 1 S-2 (35)

TABLE 3 Sensitivity Resolution Pattern Storage (J/m²) (μm) profile LERstability Example 7 350 0.13 Rectangle Δ ◯ Example 8 300 0.12 RectangleΔ ◯ Example 9 280 0.13 Rectangle Δ ◯ Example 10 250 0.12 Rectangle Δ ◯Example 11 370 0.12 Rectangle Δ ◯ Example 12 330 0.13 Rectangle Δ ◯Example 13 350 0.12 Rectangle ◯ ◯ Example 14 220 0.12 Rectangle ◯ ◯Example 15 235 0.13 Rectangle ◯ ◯ Example 16 210 0.12 Rectangle ◯ ◯Example 17 250 0.12 Rectangle ◯ ◯ Example 18 220 0.12 Rectangle ◯ ◯Comparative 650 0.15 Rectangle X X Example 1

As can be seen from Table 3, the positive-tone radiation sensitive resincomposition using the acid generator (A1) of the present inventionexcels in storage stability and base resistance, is highly sensitive,and has a high resolution as compared with the composition of theComparative Example 1 in which the acid generator (A1) is not used.

INDUSTRIAL APPLICABILITY

The sulfonium salt compound (I) of the present invention has hightransparency to deep ultraviolet rays with a wavelength of 220 nm orless and excels in base resistance, and when used as a photoacidgenerator in a chemically-amplified photoresist to be exposed to deepultraviolet rays, a resist composition with excellent sensitivity,resolution, pattern shape, LER, storage stability, and the like can beobtained.

Therefore, the positive-tone radiation-sensitive resin composition usingthe photoacid generator containing the sulfonium salt compound (I) as anessential component is extremely useful as a chemically-amplified resistfor manufacturing semiconductor devices, which will become more and moreminiaturized in the future.

1. A sulfonium salt compound shown by the following formula (1),

wherein R¹ represents a linear or branched alkyl group having 1-14carbon atoms, a monovalent hydrocarbon group having an alicyclicskeleton and containing 3-14 carbon atoms, a linear or branched alkoxylgroup having 1-14 carbon atoms, a group represented by —OR³ (wherein R³is a monovalent hydrocarbon group having an alicyclic skeleton andcontaining 3-14 carbon atoms), a linear or branched alkyl sulfanyl grouphaving 1-14 carbon atoms, an organic sulfanyl group having an alicyclicskeleton and containing 3-14 carbon atoms, a linear or branched alkanesulfonyl group having 1-14 carbon atoms, or an organic sulfonyl grouphaving an alicyclic skeleton and containing 3-14 carbon atoms, two ormore R¹ being either the same or different, R² represents a substitutedor unsubstituted, linear, branched, or cyclic alkyl group having 1-14carbon atoms, or two or more R² groups bond to form a monocyclicstructure having 3-14 carbon atoms or a polycyclic structure having 6-14carbon atoms, two or more R² groups being either the same or different,p is an integer of 0-7, q is an integer of 0-6, n is an integer of 0-3,and X⁻ represents a sulfonic acid anion.
 2. The sulfonium-salt compoundaccording to claim 1, wherein the group X⁻ in the formula (1) is asulfonic-acid anion of the following formula (II),R⁴—CF₂CF₂SO₃ ⁻  (II) wherein R⁴ represents a substituted orunsubstituted, linear or branched alkyl group having 1-14 carbon atomsor a substituted or unsubstituted, monovalent hydrocarbon group havingan alicyclic ring and containing 3-14 carbon atoms.
 3. Thesulfonium-salt compound according to claim 1, wherein p is 0 or 1, q is0, and n is 2 in the formula (I).
 4. The sulfonium-salt compoundaccording to claim 1, wherein p is 1, q is 0, n is 2, and R¹ is a linearor branched alkoxyl group having 1-14 carbon atoms in the formula (I).5. The sulfonium-salt compound according to claim 1, wherein p is 1, qis 0, n is 2, and R¹ represents —OR³ (wherein R³ is a monovalenthydrocarbon group having an alicyclic skeleton and containing 3-14carbon atoms) in the formula (I).
 6. The sulfonium-salt compoundaccording to claim 1, having a molar extinction coefficient at awavelength of 193 nm of 10,650 I/mol·cm or less.
 7. A photoacidgenerator comprising the sulfonium salt compound according to claim 1.8. A positive-tone radiation-sensitive resin composition comprising (A)a photoacid generator comprising the photoacid generator according toclaim 7 and (B) an acid-dissociable group-containing resin which isinsoluble or scarcely soluble in alkali and becomes alkali soluble whenthe acid-dissociable group dissociates.
 9. The positive-toneradiation-sensitive resin composition according to claim 8, wherein theresin of the component (B) has a recurring unit of the following formula(10),

wherein R¹¹ represents a hydrogen atom or methyl group and R¹²individually represents a linear or branched alkyl group having 1-4carbon atoms or a substituted or unsubstituted monovalent alicyclichydrocarbon group having 3-20 carbon atoms, or any two of R¹² groupsform, in combination and together with the carbon atom with which thesegroups bond, a substituted or unsubstituted, bridged or unbridged,divalent alicyclic hydrocarbon group having 3-20 carbon atoms, with theremaining R¹² group being a linear or branched alkyl group having 1-4carbon atoms or a substituted or unsubstituted monovalent alicyclichydrocarbon group having 3-20 carbon atoms.
 10. The positive-toneradiation-sensitive resin composition according to claim 8, wherein theamount of the acid-dissociable groups introduced into the resin (B) is5-100%.
 11. The positive-tone radiation-sensitive resin compositionaccording to claim 9, wherein any two of the R¹² groups, in therecurring unit of the formula (10) in the resin (B), form, incombination and together with the carbon atom with which these groupsbond, a substituted or unsubstituted, bridged or unbridged, divalentalicyclic hydrocarbon group having 3-20 carbon atoms, with the remainingR¹² group being a linear or branched alkyl group having 1-4 carbonatoms.
 12. The positive-tone radiation-sensitive resin compositionaccording to claim 9, wherein any two of the R¹² groups, in therecurring unit of the formula (10) in the resin (B), form, incombination and together with the carbon atom with which these groupsbond, a substituted or unsubstituted, bridged or unbridged, divalentalicyclic hydrocarbon group having 3-20 carbon atoms and the remainingR¹² group is a linear alkyl group having 1-4 carbon atoms.
 13. Thepositive-tone radiation-sensitive resin composition according to claim8, wherein the resin of the component (B) has a polystyrene-reducedweight molecular weight determined by gel permeation chromatography of1,000 to 500,000.
 14. The positive-tone radiation-sensitive resincomposition according to claim 8, wherein the resin of the component (B)has a ratio (Mw/Mn) of the polystyrene-reduced weight molecular weight(Mw) to the polystyrene-reduced number average molecular weight (Mn)determined by gel permeation chromatography (GPC) of the resin (B) of1-5.
 15. The positive-tone radiation-sensitive resin compositionaccording to claim 8, wherein the content of the component (A) is0.001-70 parts by weight for 100 parts by weight of the component (B).16. The sulfonium-salt compound according to claim 2, wherein p is 0 or1, q is 0, and n is 2 in the formula (I).
 17. The sulfonium-saltcompound according to claim 2, wherein p is 1, q is 0, n is 2, and R¹ isa linear or branched alkoxyl group having 1-14 carbon atoms in theformula (I).
 18. The sulfonium-salt compound according to claim 2,wherein p is 1, q is 0, n is 2, and R¹ represents —OR³ (wherein R³ is amonovalent hydrocarbon group having an alicyclic skeleton and containing3-14 carbon atoms) in the formula (I).
 19. The sulfonium-salt compoundaccording to claim 2, having a molar extinction coefficient at awavelength of 193 nm of 10,650 I/mol·cm or less.
 20. A sulfonium saltcompound shown by the following formula (1),

wherein R¹ represents a linear or branched alkyl group having 1-14carbon atoms, a monovalent hydrocarbon group having an alicyclicskeleton and containing 3-14 carbon atoms, a linear or branched alkoxylgroup having 1-14 carbon atoms, a group represented by —OR³ (wherein R³is a monovalent hydrocarbon group having an alicyclic skeleton andcontaining 3-14 carbon atoms), a linear or branched alkyl sulfanyl grouphaving 1-14 carbon atoms, an organic sulfanyl group having an alicyclicskeleton and containing 3-14 carbon atoms, a linear or branched alkanesulfonyl group having 1-14 carbon atoms, or an organic sulfonyl grouphaving an alicyclic skeleton and containing 3-14 carbon atoms, two ormore R¹ being either the same or different, R² represents a substitutedor unsubstituted, linear, branched, or cyclic alkyl group having 1-14carbon atoms, or two or more R² groups bond to form a monocyclicstructure having 3-14 carbon atoms or a polycyclic structure having 6-14carbon atoms, two or more R² groups being either the same or different,p is an integer of 0-7, q is 0, n is an integer of 0-3, and X⁻represents a sulfonic acid anion.